Pretty much all rental storage, shipping container, 3rd party semi trailer pool, safe deposit box type services and business agreements stipulate that the user of the arbitrary box gets to deny the owner of the arbitrary box access so long as they're holding up their end of the deal. The point is that the user is wholly responsible for the security of the contents of the arbitrary box and the owner bears no liability for the contents. This is why (well run) rental storage places make you use your own lock and if you don't pay they add an additional lock rather than removing yours.