My suspicion is that he was not properly prepared and only had that single copy of the key. Usually when police raids you they take all your physical storage media. IF he were properly prepared, he could just leave the country, and access the money from there. Maybe he doesn't do it because he fears the police take his backup away, no idea.

So most likely, both police and him are in a situation where collaboration by both is needed to get access to the bitcoins.