Mossop completed a double degree at Victoria University of Wellington and joined Buddle Findlay as a solicitor.
[3] Mossop works on public international law, and has published on maritime security, and how to reconcile economic activity in marine environments with biodiversity protection.
Mossop is a co-principal investigator on a 2021 Marsden grant "Reimagining ocean law to achieve equitable and sustainable use of marine ecosystems".
[7] She is a member of the IUCN Commission on Environmental Law,[6] and in 2019 she was nominated by the New Zealand government to the list of arbitrators and conciliators in Annex V and VII of the United Nations Convention on the Law of the Sea, and was the only non-government legal adviser of the four New Zealand nominations.
[3] Mossop's 2016 book The Continental Shelf Beyond 200 Nautical Miles jointly won the J. F. Northey Memorial Prize.