Holding the drive top up, gently pull the top half up from the bottom half. The back will rotate up as the front is connected by two plastic clips.

These clips are most easily undone by rotating the top enclosure to about 30º then lifting it up firmly.

Be careful to not let it jerk violently during separation. Once the top is removed, there isn't much of anything holding the latch mechanism in place. It would be a bummer to lose the spring, though getting the latch assembly back in place if it comes out is not too difficult, just don't lose the spring.