In this case, Rutland (a tweaker) robbed a meth dealer at his home. During the robbery, the dealer sustained injuries which prevented him from working for two months. Rutland was convicted in federal court under the Hobbs act, which makes it a crime to interfere with interstate commerce by threats or violence. The idea is that even though selling meth is illegal, it's still commerce (and since the dealer's source was in another state, it's interstate commerce).
I'm not sure what to say about that, but the Tenth circuit was good with it. Rutland also argued that he was robbing the dealer in his individual capacity rather than in his capacity as a drug dealer (I'm not making this up!), but the Tenth observed that 1- the evidence showed the dealer was targeted in part because of his meth-dealer status, and 2- even if that weren't true, intestate commerce was affected because the dealer couldn't run his business for two months and his assets were therefore depleted.