Petra specializes in domestic and international human rights, public and private comparative law, and international commercial law with an emphasis on international commercial contracts and dispute resolution. She has published extensively in those areas (including together with Andrew Butler, The New Zealand Bill of Rights Act 1990: a commentary (2nd ed, Lexis Nexis, 2015) and together with the late Professor Peter Schlechtriem, UN Law on International Sales (2nd ed, forthcoming)) and regularly is invited to speak at conferences, workshops, and seminars.