As an all-round EU lawyer, Gijs is at home in the broad field of European law, with state aid, internal market and market regulation as his specialties. He has many years of experience in providing legal assistance to governments and companies in these areas. Among other things, he advises parties on area developments, financing, public-private partnerships, energy regulation and issues at the interface of market and government. He also litigates regularly on a variety of European law issues and regulations.

Gijs studied European law at Utrecht University and the College of Europe in Bruges. He joined the legal profession at Pels Rijcken in 2010, before transferring to BarentsKrans in 2017. After a five-year period as EU law specialist and sector head at the Advisory Division of the Council of State, he returned to the legal profession. Since December 2024, Gijs has been with Straatman Koster advocaten, where he was appointed partner in 2025.

Gijs is a much sought-after author in the field of European law and state aid in particular. Gijs is also an editor of the Dutch Journal of European Law (NtEr) and a board member of the Dutch Association for European Law (NVER).