The United Kingdom and France established "international zones" or "control zones" at both ends of the Channel Tunnel, which crosses underneath the English Channel. British authorities exercise authority within the control zone on the French side, and French authorities exercise authority within the control zone on the UK side. Violations in the control zone are treated as if they occurred within the territory of the adjoining state within that zone, and extradition is not required to remove a violator to the operating state for prosecution.