Xavier has been a lawyer at the Paris Bar since 2001. His main areas of activity and expertise cover, in advice and litigation, public business law (public contracts, public contracts, lease contracts, land occupancy), urban planning law (building permits, pre-emption, development, planning, liability and participation in urban planning) and environmental law (circular economy, I.C.P.E. and mining law).

He advises and represents a clientele of private individuals (groups, E.T.I. and SMEs, civil companies, associations) and public (local authorities and E.P.C.I., public establishments, G.I.P.), more particularly in the sectors of public works and construction, energy, waste, transport, heritage and telecommunications. He regularly writes articles in specialized journals.

Xavier also works in local government law (administrative police, intermunicipal, relationship with satellites), general administrative law (regulated activities) and constitutional law (Q.P.C.).

Before joining Squair, Xavier was an associate at the law firm Matharan Pintat from 2001 to 2004, then at SCP Lyon-Caen & Thiriez (lawyers at the Council of State and the Court of Cassation) from 2004 to 2018. He then created his structure (XB lawyer). In 2023, as a counsel, he launched the public law/urbanism/environment practice in the Paris office of Kramer Levin LLP (which joined Morgan Lewis Bockius LLP in 2025).