Method for protection against the theft of a combustion engine vehicle with a power supply and an antitheft system

The engine operates while a radio receiver (14) passivates the anti-theft device (11) associated with the engine. The radio receiver gathers and processes an identification signal sent by a portable device (1) carried by the user. When the signal is not received a timer smoothes transient losses, then the anti-theft device progressively stops (22) the engine.