There are certain advantages that accrue from attending law school. For example, if you've just committed first degree robbery, and have been caught by the police, you're unlikely to tell them -- as Del Ugalino did here -- that "you can't arrest me for ripping off a drug dealer." For while we don't expressly teach the contrary rule, I'm pretty sure that most law students know the scoop.
Lest there be any doubt: Even if the thing you're stealing is illegal, you can still be convicted. Especially if, as here, you point a gun in someone's face to do so. Something that Ugalino gets to ponder for a dozen-plus years.