A lock for an access point such as a window includes a dual-action locking mechanism with a locking unit and a blocker. The locking unit is movable between a locking position and an unlocking position. The blocker blocks movement of the locking unit when the blocker is in a blocking position, and permits movement of the locking unit when the blocker is in an unblocking position. The lock may capture an insert attached to a tether to permit partial opening of a window while the unit is locked.