Unified Patent Court's opt-out provisions

Proprietors of and applicants for European patents have the possibility to opt out their European patents or patent applications from the exclusive competence of the Unified Patent Court (UPC). An opt-out most notably prevents a competitor from challenging the validity of the European patent centrally before the UPC (by filing an action for revocation before the UPC), thus allowing the proprietor to avoid putting all his eggs (i.e., all national parts of the European patent) in one basket.

Source: Wikipedia — Unified Patent Court's opt-out provisions (CC BY-SA 4.0)