Professional practice

Gretta has a broad practice, covering commercial litigation, domestic and international arbitration, and public international law. She has particular experience in high-value, complex ‘heavy fraud’, commercial and arbitral disputes (which often include issues relating to insolvency; and banking and finance) in the Commercial Court, off-shore jurisdictions, and before international arbitral tribunals. Her commercial and international arbitration experience includes proceedings under the LCIA, PCA, SCC, UNCITRAL and LMAA rules. She also has experience with UK arbitration-related ancillary court proceedings. Gretta appears as sole and junior counsel, and has recently appeared unled in the High Court on defended injunctive and other interim applications.

Highlights of Gretta’s current and recent work include:

  • Destin v Saipem [2024] – acting for the Applicant in a s. 9 Arbitration Act 1996 application, seeking a stay of court proceedings (led by Ben Juratowitch KC).
  • NMC plc v Shetty and Ors: acting for the lead Defendant in proceedings before the ADGM Court of First Instance in respect of multi-billion dollar insolvency and fraud claims arising out of the collapse of NMC Healthcare (led by Ruth den Besten KC).
  • Acting as junior counsel for the claimant in a multi-billion dollar PCA investment treaty arbitration for mistreatment of an investment in an Asian telecommunications market (ongoing – led by Toby Landau KC and Lucas Bastin KC).
  • Suppipat v Narongdej [2023] EWHC 1988 (Comm) (Commercial Court, 2020-2023): acting as junior counsel for the primary defendant in a c. $2billion multi-party fraud claim arising out of the sale of Thailand’s largest renewable energy firm, tried over 20 weeks from October 2022 to March 2023, and one of the Top 20 Cases for 2022.

Further to her core practice, Gretta has a particular specialization in public international law and international human rights law. She was instructed to assist New Zealand in its statements before the ICJ in the Climate Change Advisory Opinion in 2024. She was also instructed, in 2022, as junior counsel for the Defendant in an ad hoc inter-state arbitration constituted under Annex VII to UNCLOS, concerning compliance with environmental standards under that Convention; and she is currently instructed as junior counsel in relation to a complaint before the ECHR. Prior to joining Essex Court Chambers, she was a  Senior Legal and Policy Officer for a leading UK international law, where in the course of her role she assisted with and she appeared on behalf of the NGO in the European Court of Human Rights Grand Chamber case, Hanan v Germany.

Before coming to the Bar in England, Gretta qualified in New Zealand, where she practiced   for three years as a junior barrister in one of New Zealand’s leading sets, Shortland Chambers. There, she appeared both led and unled in a variety of matters, including appearing as junior counsel in a number of High Court trials (including in one of NZ’s longest running SFO prosecutions) and before the Court of Appeal. She worked as a judges’ clerk to the New Zealand Court of Appeal for two years prior to that.

Gretta obtained her LLB(Hons) at the University of Auckland, where she graduated second in her cohort and went on to read for the Bachelor of Civil Law at the University of Oxford, where she obtained a   distinction and a subject prize.

 

Arbitration & related court applications

Gretta has experience in commercial arbitration, investor-state arbitration, LMAA arbitration, and arbitration-related court applications, concerning arbitrations under a wide variety of arbitral rules (e.g. LCIA, PCA, SCC, UNCITRAL).

Investor-state

  • Junior counsel on behalf of the Claimant in a multi-billion dollar investment treaty claim in relation to mistreatment of an investment in the Indian telecommunications market. The claim raises issues of mistreatment, composite breach and significant questions of quantification in which Gretta was heavily involved. The matter has been long-running, with Gretta’s involvement since 2022. Led by Toby Landau KC and Lucas Bastin KC.
  • Junior counsel on behalf of the Claimant in an urgent measures application brought by a multi-sector investor in a State in the Caucasus region, under a bilateral investment treaty. The urgent measures application arose out of steps connected to insolvency proceedings commenced in the State in relation to the investment. Led by Sam Wordsworth KC and Lucas Bastin KC.
  • In practice in New Zealand, Gretta assisted in the conflict of laws components of a large UNCITRAL arbitration seated in Singapore. The claim concerned product liability allegations arising out of a supply agreement between multi-national companies.

Commercial arbitration

  • Junior counsel in an LMAA arbitration seeking enforcement of coverage against Underwriters, in relation to off-shore well drilling technology. Led by Neil Hart KC.
  • Instructed in an application under the Arbitration Act and LCIA rules in an LCIA arbitration concerning quantification in relation to an arbitral award, raising complex issues of valuation on the DCF-methodology. Led by Paul Key KC.
  • Assisted a Member of Chambers in respect of an LCIA arbitration relating to disclosure to underwriters;
  • Assisted a Member of Chambers in relation to enforcement of a PCA Award, including the lifting of a 103 stay and the payment of security;
  • Assisted a Member of Chambers in drafting in respect of the question of the arbitrability of company law and insolvency claims;
  • Assisting a Member of Chambers in the context of a threatened LCIA arbitration by way of derivative action;
  • Assisted a Member of Chambers in the conclusion of Memorials in respect of an ICC arbitration.

Court applications

  • Junior counsel for applicant in a s. 9 Arbitration Act 1996 application, seeking a stay of parallel court proceedings, concerning misrepresentation and rescission allegations in relation to the settlement of disputes connected to pipeline and drilling projects in Africa. Led by Ben Juratowitch KC.
  • Assisted in drafting and preparation for a number of ex parte anti-suit injunction hearings in respect of foreign proceedings taken in breach of an arbitration agreement in respect of Nevada, Massachusetts and Texan proceedings and in respect of return date hearings for the same;
  • Assisted a Member of Chambers in concluding advice as to the prospects of an appeal against an arbitral award under ss 67 and 68 of the Arbitration Act

Alongside her practice experience, Gretta has assisted in editing Russell on Arbitration and has, through that role, an extensive grasp on the current law pertaining to the Arbitration Act 1996, and the new Arbitration Act 2025.

Banking & financial services

In many of her long-running, high-value cases in the Commercial Court and in arbitration, Gretta has been heavily involved in have raised issues of banking, financial services, or claims against banks. In particular:

  • NMC plc v Shetty and Ors: acting for the lead Defendant in proceedings before the ADGM Court of First Instance in respect of multi-billion dollar insolvency and fraud claims arising out of the collapse of NMC Healthcare (led by Ruth den Besten KC). The claimant has also brought claims against Bank of Baroda and raised issue of banking practices and the internal management of corporate bank accounts and banking guarantees.
  • Acting as junior counsel for the claimant in a multi-billion dollar PCA investment treaty arbitration for mistreatment of an investment in an Asian telecommunications market (ongoing – led by Toby Landau KC and Lucas Bastin KC). The arbitration has raised questions relating to financing and refinancing terms, bank approvals and market lending practices.
  • Suppipat v Narongdej [2023] EWHC 1988 (Comm) (Commercial Court, 2020-2023): acting as junior counsel for the primary defendant in a c. $2billion multi-party fraud claim arising out of the sale of Thailand’s largest renewable energy firm, tried over 20 weeks from October 2022 to March 2023, and one of the Top 20 Cases for 2022.

Outside of her heavy commercial and investment cases, she has advisory experience in relation to banking and finance matters, including on pupillage:

  • Assisting in drafting analysis as to the proper law of alleged misrepresentation claims in respect of LIBOR fixing;
  • Assisting in pleading a claim of fraud and unlawful means conspiracy against a former employee of a leading bank;
  • Assisting in case management in relation to a complex fraud claim against former directors of a foreign bank;
  • Assisting a Member of Chambers in relation to fraud claims arising out of mortgage-backed security schemes.
  • Assisting a Member of Chambers in relation to jurisdictional challenges to matters arising out of funding agreements between a Russian bank and an oil refinery.
  • Assisting a Member of Chambers in respect of advice as to the regulation and investment management in the context of funds under the Undertakings for Collective Investment in Transferable Securities directive, the Alternative Investment Fund Managers Directive and relevant FCA regulatory requirements of the same.
  • Assisting in drafting and attending the return date in respect of an urgent injunction restraining the use of confidential information, following the completion of an internal investigation by a leading financial services institution.

In practice in New Zealand, Gretta acted a junior counsel in the defense of a complex fraud prosecution against former directors of a finance company by the NZ SFO, in relation to allegations of related- party lending and breaches of a Crown Guarantee.

Civil fraud & asset recovery

Gretta has acted in high-value and complex civil fraud cases, which alongside issues of fraud, have raised blended issues of insolvency, commercial chancery and banking and finance issues. In the last three years, Gretta has been heavily engaged as junior counsel in two heavy, long-running civil fraud matters, based in the Commercial Court and in the ADGM:

  • NMC plc v Shetty and Ors: acting for the lead Defendant in proceedings before the ADGM Court of First Instance in respect of multi-billion dollar insolvency and fraud claims arising out of the collapse of NMC Healthcare (led by Ruth den Besten KC).
  • Suppipat v Narongdej [2023] EWHC 1988 (Comm) (Commercial Court, 2020-2023): acting as junior counsel for the primary defendant in a c. $2billion multi-party fraud claim arising out of the sale of Thailand’s largest renewable energy firm, tried over 20 weeks from October 2022 to March 2023, and one of the Top 20 Cases for 2022.

These instructions have built on her experience gained during her pupillage with James Willan KC, in which Gretta assisted in a number of civil fraud matters, including at the case management, interim application and trial stages. Examples include:

  • Assisting in drafting and in the hearing of a three-week Family Court  hearing against the unlawful assistance of a son to his father by participating in actions intended to defeat the interests of creditors;
  • Assisting in drafting a pleading in respect of Dutch tort law claims in the context of fraud committed by an employee against his employer, a Bank, for alleged bribes;
  • Assisted a Member of Chambers in drafting in respect of an application for an order setting aside various rulings in the context of an unlawful means conspiracy claim between a
  • Russian Bank and an oil Refinery, including in relation to jurisdiction, additional claims and expert Russian law evidence.
  • Assisting a Member of Chambers in relation to an application to discharge or reduce the quantum of a freezing order in relation to US45 million of assets frozen and a related application for fortification of a cross-undertaking as to damages;
  • Assisting in the preparation for and attendance in respect of a Part 71 Judgment Debtor cross-examination in assessment of assets to satisfy judgment.
Commercial chancery disputes

Gretta has a range of commercial and chancery-related experience, including in connection to her civil fraud practice, which have raised fraud in the context of the breach of director’s duties, company law, and issues concerning the scope and application of s. 432 of the Insolvency Act.

She appears regularly, unled, in the Chancery Division of the High Court, in relation to defendant interim applications and injunction applications. She is instructed as sole counsel in an ongoing dispute between former joint venturers in relation to a business operating on the blockchain, raising issues of breach of confidence and defending a claim for a final injunction.

Further experience includes:

  • Assisting a Member of Chambers in respect of a strike out application in the context of a claim for unfair prejudice, winding-up proceedings and breach of directors’ duties;
  • Assisting a Member of Chambers in respect of an appeal in the context of the arbitrability of a winding-up petition and the nature of the Court’s jurisdiction in respect of the same;
  • Assisting a Member of Chambers in drafting an unfair prejudice and winding-up petition.

Gretta’s commercial chancery experience extends through to her time practicing in New Zealand, where she appeared as junior counsel in a long-running High Court trust dispute, acting for the executors of a trust in response to allegations of breach of fiduciary duty, mismanagement of trust assets and the enforcement of a constructive trust. She also appeared as junior counsel in a shareholders’ dispute in respect of the sale of a software company.

Commercial dispute resolution

Gretta has a range of experience involving commercial dispute resolution, both in New Zealand and during pupillage, including tort, contract and unjust enrichment claims.

She was junior counsel for the primary defendant in Suppipat v Narongdej [2023] EWHC 1988 (Comm) (Commercial Court, 2020-2023): a c. $2billion multi-party fraud claim arising out of the sale of Thailand’s largest renewable energy firm, tried over 20 weeks from October 2022 to March 2023, and one of the Top 20 Cases for 2022.

She was instructed as junior counsel on NMC plc v Shetty and Ors, acting for the lead Defendant in proceedings before the ADGM Court of First Instance in respect of multi-billion dollar insolvency and fraud claims arising out of the collapse of NMC Healthcare (led by Ruth den Besten KC).

Her experience in the Commercial Court and in off-shore jurisdictions on commercial matters supplements her experience in international and commercial arbitration, which raise similar issues, including as to questions of quantification and valuation, with which Gretta is well-versed.

Further experience includes:

  • Assisting in drafting argument resisting further disclosure in the context of a dispute as to ownership of the proceeds of an Initial Coin Offering in respect of a Cryptocurrency exchange platform between directors;
  • Drafting a Defence to an alleged breach of an exclusive mandate in a Facility Agreement in the context of financing for the acquisition of a Refinery;
  • Assisting a Member of Chambers in drafting and commencing proceedings as to unfair prejudice in respect of exclusion of a shareholder and director following a merger and acquisition;
  • Assisting in drafting and attending a hearing in respect of strike-out proceedings in relation to an unlawful means conspiracy claim against a former director for breaches of fiduciary duty;
  • Assisting in drafting a defence to a claim for debt and for damages in the breach of contract in relation to the dissolution of a joint commercial enterprise, including complex issues of contractual interpretation;
  • Assisting in advising in respect of a telecommunication framework agreement;
  • Assisting in drafting and attending the return date in respect of an urgent injunction restraining the use of confidential information.

In New Zealand, Gretta acted as junior counsel in a case alleging unlawful means conspiracy in an employment context in a case in which she assisted in pleading, interim measures and further disclosure hearings. She appeared as sole counsel in a High Court application, defending against summary judgment in the enforcement of contractual guarantees.

Conflict of laws & private international law

Gretta has a particular interest in private international law, following her undergraduate studies, and work in New Zealand on questions of choice of law and the limits of   the mandatory application of public policy law of the forum in the context of both domestic and international arbitral disputes.

Many of Gretta’s cases to date have concerned claims arising in multiple jurisdictions, or are cases with an international or trans-jurisdictional component. Questions of conflict of laws (and related issues of proper forum and service out) are frequent and are matters with which she is well-versed. She is experienced in handling handling foreign law and working with and assisting with the cross-examination of foreign law experts (including Thai law (Suppipat); Abu Dhabi law (NMC v Shetty), issues of Indian law and Georgian law). She has acted in and is well-versed in arbitration-related court applications concerning the question of jurisdiction and related s.9 stays; and she has assisted in editing Russell on Arbitration, with a particular focus on the proper law of the arbitration agreement.

Alongside her conflict of laws experience in the course of her core commercial practice, further examples include:

  • Assisting a Member in advice as to proper law analysis of misrepresentation claims in a financial services context;
  • Assisting a Member in an application setting aside various rulings in the context of a widespread civil fraud dispute, including service out and forum conveniens issues;
  • Assisting a Member in seeking a stay of proceedings in the context of lis alibi pendens and res judicata.
Energy & natural resources

During pupillage, Gretta assisted in relation to a number of disputes in relation to energy and natural resources, including:

  • Assisting a Member of Chambers in advising as to a contractual dispute in relation to the funding and purchase of a gold mine;
  • Assisting a Member of Chambers in relation to a contractual dispute relating to the shipping of oil, including the recovery of liquidated damages, termination for repudiatory breach and the provision and enforcement of payment terms on a letter of credit;
  • Assisting a Member of Chambers in relation to insurance claims arising in respect of African mining permits;
  • Assisting a Member of Chambers in relation to financing in respect of the purchase of an oil refinery;
  • Assisting a Member in respect of commercial conspiracy claims arising from alleged double-selling of oil transshipments.
European law & competition

In the course of her post-graduate studies, Gretta has been exposed to a number of areas of law that touch on European regulations. She is well-versed in European constitutional law and has studied European regulations relating to air quality, water and counter-terrorism measures, including terrorist financing.

Human rights & civil liberties

Gretta has a particular specialization and academic experience in human rights law. She has experience in both advisory,  strategic and litigious steps relating to human rights and civil liberties, both domestic and international.

Gretta is currently instructed in an EHCR claim (led by Malcolm Shaw KC) in a claim against Romania, relating to alleged breaches of Art. 6. Prior to coming to the Bar, she assisted  with and appeared in an intervention on behalf of a leading international law charity in the Grand Chamber hearing of Hanan v Germany at the ECHR, where she attended as representative, and similarly concluded a written intervention in respect of HF and MF v France, which has since been relinquished to the Grand Chamber.

In her advisory practice and in the course of her employment with Rights and Security International, she advised in respect of domestic judicial review actions at the High Court and Supreme Court level pertaining to human rights claims, as well as advising on foreign constitutional actions and claims to international courts and judicial bodies of the United Nations, including the UN Committee on the Rights of the Child and the UN Working Group on Arbitrary Detention.

At Oxford, Gretta received the award for the Highest Achieving Student in Criminal Justice, National Security and Human Rights, comprising questions of the extra-territoriality of human rights obligations, as well as human rights in the context of police use of force, extrajudicial killing and drone strikes.

Insurance & reinsurance

Within her broad commercial practice, Gretta has developed a practice in insurance and reinsurance disputes. This includes:

  • Instructed as junior counsel in an LMAA arbitration, in relation to the enforcement of an insurance policy against underwriters in relation to off-shore well drilling machinery (with Neil Hart KC).
  • Advising in relation to a COVID BI interruption claim for a hospitality business (with Jeffrey Gruder KC).
  • Instructed as junior counsel in relation to an arbitral claim on behalf of underwriters against reinsurers, in a multi-million euro dispute arising out of a quota share reinsurance contract (with David Peters KC).

Her further experience includes:

  • Assisting a Member of Chambers in an LCIA arbitration concerning questions of material nondisclosure to underwriters; and
  • Assisting a Member of Chambers in concluding advice in relation to liability under an Excess of Loss Liability Policy on the Bermuda Form.
Public & administrative law

Gretta has experience in public and administrative law, having studied both public and administrative law at an undergraduate level and completing her honours course in Public Law. She is a member of the Government Legal Department Junior Juniors Scheme.

In practice in New Zealand, she acted as junior counsel on a number of judicial review matters. Prior to joining Essex Court, Gretta led on domestic judicial review actions taken by the Rights Watch UK and advised in respect of a number of other contemplated actions.

Gretta also has exposure to FOIA and Independent Police Complaints Commission processes, having assisted and advised in the compilation of such requests and challenges in her role with Rights Watch UK. She also worked on and assisted in relation to appeals against measures depriving individuals of citizenship.

Public international law

Gretta has a particular interest and expertise in Public International Law. She has been instructed to act for and against states in a number of her cases, and much of work raises questions of international law, or involve issues of an international or cross-border nature.

Her recent instructions include:

  • Acting for and advising New Zealand in relation to the written phase of the ICJ Climate Change Advisory Opinion.
  • Assisting in the drafting of advice relating to the Crime of Aggression in relation to Russia’s invasion of Ukraine (with Dapo Akande).
  • Acting as junior counsel for the Defendant in the Coastal States Rights ad hoc inter-state arbitration constituted under Annex VII to UNCLOS, concerning, inter alia, compliance with environmental standards under that Convention (led by Sam Wordsworth KC and Amy Sander).
  • She has been instructed for individual complainants and as intervenor in cases in the ECHR, including in Hanan v Germany on the specific issues of the extra-territorial jurisdiction of the Convention under Article 1.
  • She has assisted the UN Special Rapporteur on Counter-terrorism and human rights in its written intervention in HF and MF v France before the ECHR.

In 2021 and 2022, Gretta was seconded to the Foreign, Commonwealth and Development Office’s Legal Directorate, providing advice to and working with the Oceans and Overseas Territories Team. She advised in relation to a number of matters, including in relation to the British Indian Ocean Territory, UNCLOS related issues, and issues at the intersection of domestic and international human rights law.

Prior to joining Essex Court Chambers, she was a  Senior Legal and Policy Officer for a leading UK international law, where in the course of her role she assisted with and she appeared on behalf of the NGO in the European Court of Human Rights Grand Chamber case, Hanan v Germany.

Gretta has an enduring academic interest in Public International Law. In New Zealand, Gretta she prizes for the Top Student in International Law and in Advanced International Law. She completed her honours thesis in International Humanitarian Law (specifically on the  scope and limits of detention in non-international armed conflicts). She represented New Zealand at the Philip C Jessup International Law Moot Court Competition, where she was a ranked speaker; she coached the New Zealand team three years later, which won the prize for best overall Applicant team. At Oxford, she studied International Law of the Sea, International Law and Armed  Conflict, and International and Comparative Environmental Law. She was top student in Criminal Justice, National Security and Human Rights, which featured a significant component of international law and has a particular interest in the litigation and treatment of questions of international law and state immunity in domestic courts.

Regulatory law & investigations

In practice in New Zealand, Gretta acted as junior counsel in respect of regulatory matters, including at the investigation or pre-prosecution stages, both in relation to Education Act regulatory matters and Serious Fraud Office regulatory prosecutions.

Shipping & admiralty

Gretta continues to develop her shipping and admiralty law practice. She is presently instructed on a Marine Insurance Act LMAA arbitration with Neil Hart KC.

Her further experience includes:

  • Drafting a defence in respect of a Marine Insurance Act 1906 claim; and
  • Assisting a Member in respect of advice on a challenge to the admiralty jurisdiction in respect of the arrest of a ship.
Unjust enrichment & restitution claims

Many of the disputes in which Gretta is instructed raise issues of unjust enrichment and restitution. Examples include:

  • Instructed as junior counsel in a s.9 Arbitration Act application, seeking a stay of a parallel claim raising issues of rescission and restitution.

During pupillage, Gretta assisted in drafting a claim for unlawful means conspiracy including claims for restitution in Dutch law.

Career

2021 – Tenant, Essex Court Chambers

2021 – Called to the Bar (Lincoln’s Inn)

2020-2021 – Pupillage, Essex Court Chambers (with James Willan KC)

2019-2020 – Senior Legal and Policy Officer, Rights and Security International (Rights Watch UK).

2016-2018 – Junior Barrister to Shortland Chambers, New Zealand

2015 – Called to the Bar, New Zealand.

2014-2015 – Judges’ Clerk to the Court of Appeal of New Zealand

Education

2018-2019 – University of Oxford, BCL (DIst)

2009-2014 – University of Auckland, BA/LLB (Hons) (BA: German and Philosophy)

Awards

University of Oxford:

  • Faculty of Law Prize for Top Student in Criminal Justice, National Security and Human Rights
  • Yvonne Smith Fellowship Recipient 2018

University of Auckland:

  • Senior Scholar Award, Arts;
  • Senior Scholar Award, Law;
  • F A De La Mare Memorial Prize ( best academic record in third, fourth and fifth year LLB cohort);
  • First in Course Award – Advanced International Law;
  • JP Campbell Bursary Prize (best student achievement in any two final year papers in LLB cohort);
  • Faculty of Law Dean’s Academic Excellence Award;
  • First in Course Award – Company Law;
  • First in Course Award – International Law;
  • Desmond Lewis Memorial Prize in International Law
  • Senior Prize in German.
Publications
  • Just Security, “The Shamima Begum Decision: What Could It Mean for Other ISIS Women and Children Unable to Repatriate?”, 3 August 2020.
  • Contributing author, Hon Justice Mathew Downs (ed) Cross on Evidence (10th ed, 2017, LexisNexis, Wellington).
  • Jenny Cooper KC and Gretta Schumacher “Gender Ratio of Counsel Appearing in Higher Courts” (September 2018), New Zealand Bar Association and New Zealand Law Foundation funded research project.
  • New Zealand Journal of Taxation Law and Policy “Taxing or Relaxing: the Deductibility of Expenditure on Holiday Homes, Boats and Aircraft” (2016), 22 (vol 1) NZJTLP 47.