“Well regarded for her work on international child abduction cases. Dispenses excellent advice. Very dogged and knowledgeable yet very down to earth. ”

Legal 500


Onyója is a leading junior and academic expert in international child and family law. She was a finalist for Rising Star – Barrister/Advocate of the Year in the Women in Law Awards 2020 and has been consistently ranked in the Legal 500 UK for children law since 2017. She regularly appears in the High Court (Family Division), at all levels of the Family Court and the Court of Appeal. She also receives instructions to provide expert opinions in proceedings in the UK and abroad, as well as being an invited expert presenting at forums such as the Hague Conference on Private International Law (HCCH) and the UK House of Lords Justice and Home Affairs Committee.

The Legal 500 2024 once again recognises Onyoja as an children law expert, stating that ‘Onyoja is always on point and well-versed in the areas of law. She is always very well prepared and does her research. She is a very experienced litigator, approachable and helpful.’

Alongside practice at the Bar, in 2014 Onyója was awarded the prestigious Elphinstone PhD scholarship to undertake her doctoral research at the University of Aberdeen, examining domestic and family violence in the context of the Article 13(1) b) exception of the 1980 Hague Child Abduction Convention, supervised by Dr Katarina Trimmings and Professor Paul Beaumont. Her research included empirical work interviewing judges and Central Authorities in EU civil law and common law jurisdictions and Reunite, culminating in policy recommendations to the Hague Expert Working Group on Article 13(1) b) (chaired by the Rt Hon. Diana Bryant (Australia) with committee members including Lady Hale of Richmond DBE (former President of the Supreme Court), a paper at the 7th JPIL conference in Rio, Brazil and publication of part of her research in the leading peer-reviewed journal.

Onyója is a lecturer in private international law at the University of Aberdeen, having previously undertaken a post-doctoral fellowship as the UK research assistant on the major collaborative EU-funded POAM project. The project included a core consortium: UK, Croatia, Germany and Italy, and points of contact in Spain, Serbia and Slovenia. She has published in peer-reviewed journals, delivered training, lectures and papers around the world on international family law, with a focus on child rights and gender equality issues. Recent and upcoming publications include a book chapter entitled "The Need for Cross-Border Protective Measures in Return Proceedings" in Trimmings K, Dutta A, Honorati C and Zupan M (eds), "Domestic Violence and Parental Child Abduction" (Intersentia 2022); O Momoh, 'The challenges of the Hague Convention on International Child Abduction, in particular in cases of domestic and family violencein J Antomo, K Duden, D Wiedemann (eds), Changing families, changing family law – Convergence or divergence in Europe (Intersentia 2023); and O Momoh, Intercountry adoption: preventing and addressing illicit practices in intercountry adoption’ in J M Carruthers and B Lindsay (eds) in Research Handbook on International Family Law, (Edward Elgar Publishing, 2023).  

In September 2023, Onyója's book "A Practical Guide to International Parental Child Abduction Law (England and Wales)" was published by Law Brief Publishing cementing her status as one of the forefront experts in this area. 

   The Legal 500 - The Clients Guide to Law Firms  Uk Leading Junior 2023 

International family law

Onyoja's expertise lies in cross border proceedings involving the Hague Children's Conventions including the 1980 child abduction, 1993 inter-country adoption and 1996 child protection conventions, as well as non-Hague cases; the recognition of foreign adoptions, relocation, and other jurisdictional disputes including technical points of law such as forum conveniens and parens patriae jurisdiction. She has a strong international practice and is well known for this type of work, including instructions from abroad to provide English legal expert reports. 

She has been involved in cases with significance such as the High Court decision in Re R v B (Stranded: Habitual Residence: Forum Conveniens [2020] [EWHC] 1041 (Fam) that found three children stranded in the Kingdom of Saudi Arabia for three and a half years to have no county of habitual residence, or the English court’s recognition of a Ugandan foreign adoption order which was adopted as precedent under Ugandan law in MDK v NA [2020] EWHC 1548 (Fam). She has advised pre-proceedings and successfully represented a ‘left behind’ father in his application under Art 11(6)-(8) Brussels IIa following a Hague non-return order made by the Court of Appeal in Poland. Uniquely complemented by her post-doctoral academic and research background, Onyoja has a natural ability to think creatively and approach multi-layered international cases with ease.

Children law (public)

Onyoja’s core children act practice is in public law, regarded as an advocate “with great skill and care”, “dealing thoroughly yet proportionately with the issues”. She is forensic and particularly experienced in complex international care proceedings involving assessments and placements abroad, as well as cases involving honour based violence including the risk of death, FGM, missing children, child abuse and non-accidental injuries and domestic violence. She receives instructions to act for parents, relatives, children (through their guardians), the local authority and other intervenors, appearing in proceedings at all stages especially those involving vulnerable children and parents, in care and adoption proceedings; wardship applications - stranded spouse, forced marriage protection orders, FGM and other applications under the court’s inherent jurisdiction.  

Children law (private)

Onyoja accepts instructions in all applications made in respect of children under the Children Act 1989, particularly where there is an international element. Her breadth of practice involves representing clients in applications for a child arrangements order, specific issues, to vary or enforce contact and access, special guardianship, as well as applications for temporary or permanent leave to remove children from the jurisdiction to Hague and non-Hague convention countries. She has acted in cases that have presented issues of jurisdiction and habitual residence, as well as cases that encompasses injunctive relief for the family.

Human rights (GBV and child rights)

Onyója’s funded PhD by research focused on domestic and family violence in the context of 1980 Hague Convention proceedings, she has also undertaken assignments as UN volunteer for a grassroot charity combating GBV and VAWG in Papua New Guinea. Her ongoing work on the EU funded POAM project, has contributed to the drafting of the Best Practice Guide and Executive Summary on Regulation (EU) 606/2013 & the 1996 Hague Convention on protective measures for mothers against the backdrop of domestic violence, the UK national report, as well as presenting in Brussels, organising experts’ local and international workshops, including as a trainer. Her well-rounded experience, both in policy and practice with an international dimension, makes her particularly skilled and knowledgeable in this area.

Private international law (Africa)

Onyója is the inaugural chair of the Nigeria Group on Private International Law (NGPIL), an initiative that she spearheaded to bring together experts to improve PIL in Nigeria, and Africa. Recent endeavours have included a joint mission with the Secretary General of the HCCH, Dr Christophe Bernasconi, to Abuja in 2021. She is also a past committee member of the British Nigeria Law Forum.

She has a family law practice that engages countries in Africa such as Nigeria, Ghana, South Africa, Sierra Leone, Somalia, Uganda, South Africa and Madagascar. She has written for the Africa Portal and is currently developing collaborative research to strengthen child protection including combating child trafficking in the context of inter-country adoption in Nigeria, with the aim of persuading Nigeria to adopt the HCCH Children Conventions (1980, 1993, 1996 and 2007).

Publications & Papers

Dr O Momoh "A Practical Guide to International Parental Child Abduction Law (England and Wales)"

O Momoh, ‘The need for cross-border protective measures in return proceedings’ in Trimmings K, Dutta A, Honorati C and Zupan M (eds), Domestic Violence and Parental Child Abduction (1st edn, Intersentia 2022)

K Trimmings, O Momoh, 'Intersection between Domestic Violence and International Parental Child Abduction: Protection of Abducting Mothers in Return Proceedings' (2021) Vol 35, Issue 1, International Journal of Law, Policy and The Family, 1–19

UK Training Workshops – POAM Best Practice Guide (the utility of the 1996 Hague Convention: jurisdiction, recognition and enforcement), Co-Trainer (December 2020)

O Momoh, ‘Why Nigeria should welcome the value and feasibility of acceding to the Hague Conference Children’s Conventions” (2020) Africa Portal, expert analysis hub.

O Momoh, ‘The recognition at common law of Nigerian adoption orders in the UK and the role of the 1993 Hague Convention on Intercountry Adoption in Nigeria: learning from Re V (A Child) (Recognition of Foreign Adoption) [2017] EWHC 1733 (Fam)’ (2020) 28, Journal of Law, Policy and Globalisation, 129-134

Conference paper – 23rd Annual Family Law Conference MdT/UWC, Cape Town, South Africa, March 2020, Speaker (Child Abduction: The “POAM Project”, EU funded research). International Grant Award, Bar Council and FLBA

POAM International Experts Workshop, Co-Moderator – “Rethinking the Protection of Abducting Mothers in Return Proceedings: Domestic Violence and Parental Child Abduction” (June 2020).

O Momoh, 'The interpretation and application of Article 13(1) b) of the Hague Child Abduction Convention in cases involving domestic violence: Revisiting X v Latvia and the principle of “effective examination”' (2019) 15(3) Journal of Private International Law, 626-657

K Trimmings, O Momoh, I Callander ‘Protection of Abducting Mothers in Return Proceedings: Intersection between Domestic Violence and Parental Child Abduction: UK National Report’ (2019) EU funded report.

O Momoh, ‘The Approach by Judges to the Assessment of the Grave Risk of Harm in Cases Involving Domestic Violence’ (December 2018) 11 (1) International Bar Association, 9-11

O Momoh ‘Domestic Abuse in the Drafting of Article 13(1) b of the 1980 Hague Convention on the Civil Aspects of International Child Abduction’ (2017) 2(1) The Hague University, ILSA Law Journal, 11-17

Seminar paper ‘Parental child abduction: lessons learnt from Contracting States to the 1980 Hague Convention and a way forward for Nigeria’ British Nigerian Law Forum (2017) speaker and organiser.

Seminar paper: 'An Exploration of Child Rights in Nigeria’ (2016) BHRC and Coram Children’s Legal Centre.

Paper: 'New Laws in Relation to Stalking, Child Protection and Employer Responsibility' (2015) Global Foundation for Elimination of Domestic Violence.

Paper: ‘The Clue is in the Name: The Court of Protection’ (2013) Leigh Day


To instruct Onyoja please contact Jay Dorton or Stephen Bush


  • 2014-2018 PhD in Law (Private International Law of Family Law), research title: “Domestic and Family Violence in context of the 1980 Hague Convention on the Civil Aspects of International Child Abduction” University of Aberdeen
  • 2012 LL.M (thesis on international child abduction - 1st class), University of London, City
  • 2010 Bar Vocational Course, City Law School, London
  • 2009 BA (Hons) Economics & Law, University of Leicester


  • Family Law Bar Association
  • Child Abduction Lawyers Association (past committee)
  • Centre for Private International Law, University of Aberdeen (Research and Teaching Fellow)
  • British Nigeria Law Forum (past committee)
  • The Honourable Society of Gray's Inn


  • 2020 International Grant Award, Bar Council and FLBA (Cape Town, South Africa)
  • 2014 Elphinstone PhD scholarship
  • 2009 Gray’s Inn Junior Award
  • 2008 Winner of the Frances Oldham QC Prize (best overall 2nd year performance by a student intending to become a barrister)

Notable Cases

Re D [2022] EWHC 3602 (Fam): application under the inherent jurisdiction of the High Court for the recognition of foreign Guardianship Orders made in India in 2007 and 2010 in which Onyoja successfully argued that the guardianships were effectively adoption orders. 

Re D (Abduction: Article 13(b): Child in Care) [2022] EWHC 317 (Fam): representing a mother in respect of a child in care who was subject to Hague return proceedings.

GN v SN [2022] EWHC: representing a father in respect of a mother's application for the return of her children to Hungary under the Hague Convention.

Re R [2021] [EWHC] concurrent wardship and care proceedings involving complex factors, return orders and publicity orders (Madagascar).

LA v NA [2021] EWHC (Fam): recognition of a (non-Hague) foreign adoption order (Nigeria).

A (a child: fact-finding)[2021] EWFC B29: sole counsel in 3-week fact finding hearing involving non-accidental injuries to a child.

Re B [2020] High Court of South Africa (Western Cape Division): expert report in 1980 Hague Convention proceedings.

MDK v NA [2020] EWHC 1548 (Fam): recognition of a (non-Hague) foreign adoption order (Uganda).

Re FL (a Child): [2020] EWCA Civ 20: Court of Appeal decision where SGO order made in favour of a maternal grandmother ('MGM') was upheld. Representation of the mother at the 7 day Final Hearing and Appeal. In making the SGO (dismissing the LA's application supported by guardian) the court of first instance recognised counsel's assistance of MGM (unrepresented) in putting forward her case aligned with the mother's. 

Re R v B (Stranded: Habitual Residence: Forum Conveniens [2020] [EWHC] 1041 (Fam): concerning three children stranded in the Kingdom of Saudi Arabia for 3.5 years, issues of jurisdiction, habitual residence (nationality), parens patraie and forum conveniens. The court finding no habitual residence in either country.

Re M [2019] [EWHC]: enforcement of a return order from Ghana.

Re B [2019] [EWHC]: Art 12 of the 1980 Hague Convention, rights of access, representing a parent abroad, the Czech Republic.

Re M [2018] [EWHC]: Art 11(6)-(8) Brussels IIa application to address Polish court non-return order, issues of Art 15 (transfer) and Art 16 & 19 (seising of a court; lis pendens).

Re AB [2018] [FC]: leave granted to oppose the making of an adoption order under s47(5) ACA 2002

R v R [2017] [EWHC]: application for wardship and FGM protection order, Ghana.

K v L [2017]: enforcement of child arrangements order, issues of jurisdiction and habitual residence, The Netherlands.

H v F [2016] [EWHC]: temporary leave to remove from the jurisdiction of England and Wales to a non-Hague Convention Country, Thailand.

B v P [2016] [EWHC]: child abduction, jurisdictional dispute on the applicability of Brussels II Revised between the UK and Gibraltar, representing a parent abroad.

M v M [2015]: stranded case and wardship, child abduction to a non-Hague Convention country, Pakistan.

Re S [2015] [ELFC]: nine day fact finding hearing within care proceedings.

Back to people