A lock including a housing having an opening for a locking bolt, a locking bolt movable between a locked position and an unlocked position, an actuator positioned within the housing, and a rotary blocking device that prevents the locking bolt from moving to the unlocked position is disclosed. The lock may optionally include a tamper resistant mechanism that is designed such that attempting to forcibly move the locking bolt from the locked position to the unlocked position while the actuator remains in the locked condition causes the locking bolt to engage the tamper resistant mechanism.