[JURIST] The US Supreme Court [official website] ruled [opinion, PDF] Monday in Bond v. United States [SCOTUSblog backgrounder] that prosecutors cannot use an international chemical weapons treaty to convict a woman who attacked her husband’s lover. Carol Anne Bond attempted to poison the woman by applying two toxic chemicals to her mailbox, car door handles and house doorknob. She was then convicted under the Chemical Weapons Convention Implementation Act [18 USC § 229 text], a federal law that enforces the international Chemical Weapons Convention [materials], which intends to ban the spread of international chemical weapons. The US Court of Appeals for the Third Circuit upheld the conviction [opinion]. In an opinion by Chief Justice John Roberts, the Supreme Court reversed:

The question presented by this case is whether the Implementation Act also reaches a purely local crime: an amateur attempt by a jilted wife to injure her husband’s lover, which ended up causing only a minor thumb burn readily treated by rinsing with water. Because our constitutional
structure leaves local criminal activity primarily to the States, we have generally declined to read federal law as intruding on that responsibility, unless Congress has clearly indicated that the law should have such reach. The Chemical Weapons Convention Implementation Act contains no such clear indication, and we accordingly conclude that it does not cover the unremarkable local offense at issue here.

There were several concurring opinions.

The court heard arguments in the case in November after granting certiorari [JURIST reports] in January of last year. The court ruled in 2011 that Bond had standing [JURIST report] under the Tenth Amendment [text] to challenge the application of the treaty against her but did not determine the merits of her claim at that time.