Implement lock assembly for retaining batons, nightsticks, and other handheld devices within a holster. The assembly includes a base, a lock, and a release. Operation of the assembly is by a user applying pressure to the lock, pivotally moving the lock from an open position to a closed position. In the normal open position, an implement may be inserted or removed from the holster. In the closed position, the lock retains the implement within the holster. The lock may be opened by applying pressure to the release. The lock may engage and retain a baton along the length of the baton grip, allowing a user to adjust the position of the baton within the holster when the baton is retained by the lock.