A locking mechanism for the situation-dependent authorized admission or access to any casing and the protection of the casing against misuse of its contents is disclosed. The locking mechanism comprises at least one rotatable locking member (1) and at least one latch member (2) which can be unlocked by the rotatable locking member (1). In case of an emergency the latch member (2) is accessible also through a breakable barrier (3) and can be manually moved after the barrier (3) has been irreversibly destroyed.