He did label it, said it still got stolen. Idk, I'm kind of on his side here...He'd been better off by not labeling the bag with "Do not eat, poison" in the first place.
Had he just put the laxatives from day 1 with no warning he'd still get a good kick out from fucking with the thief and nobody could allege malicious intent even if things went south, and even if they did the guy could've argued he had been suffering from constipation and that would be the end of it.