Feds can't prosecute "unremarkable local offense"

That's what the Supreme Court said today in a very interesting opinion, Bond v. United States.  From Chief Justice Roberts' majority:

The horrors of chemical warfare were vividly captured by John Singer Sargent in his 1919 painting Gassed. The nearly life-sized work depicts two lines of soldiers, blinded by mustard gas, clinging single file to orderlies guiding them to an improvised aid station. There they would receive little treatment and no relief; many suffered for weeks only to have the gas claim their lives. The soldiers were shown staggering through piles of comrades too seriously burned to even join the procession.
     The painting reflects the devastation that Sargent witnessed in the aftermath of the Second Battle of Arras during World War I. That battle and others like it led to an overwhelming consensus in the international community that toxic chemicals should never again be used as weapons against human beings. Today that objective is reflected in the international Convention on Chemical Weapons, which has been ratified or acceded to by 190 countries. The United States, pursuant to the Federal Government's constitutionally enumerated power to make treaties, ratified the treaty in 1997. To fulfill the United States' obligations under the Convention, Congress en-
acted the Chemical Weapons Convention Implementation Act of 1998. The Act makes it a federal crime for a person to use or possess any chemical weapon, and it punishes violators with severe penalties. It is a statute that, like the Convention it implements, deals with crimes of deadly seriousness.
     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.

ScotusBlog has this summary:

The Court appeared to bring to an end a case that even the Justices acknowledged was a “curious” one:  a federal criminal prosecution, with a potential life sentence, of a Pennsylvania woman because she sought revenge by spreading poison chemicals on surfaces that her husband’s paramour would touch — a door knob, a car door handle, the mailbox.  The other woman did touch one of those surfaces, and got a minor burn on a thumb – dealt with by rinsing her hand with water.
Although the prosecuted woman, Carol Anne Bond, may have violated a number of laws in her state, she actually was charged under state law only for making harassing telephone calls and letters, and state officials refused to accuse her of assault.  She had pleaded guilty to the federal crime of using a “chemical weapon,” on condition that she could later challenge the prosecution. She was convicted under the 1998 law, but Monday’s decision wiped out that result because the law did not even apply to what she did, according to the Court majority.
Aside from its own unusual facts, the case had attracted wide notice because it seemed to pose the ultimate question of just how far Congress could go, in regulating activity entirely inside the U.S., when it was enacting a law to carry out a global obligation that the federal government had assumed under a treaty.  In particular, the case raised a question about the continuing validity of a 1920 precedent, Missouri v. Holland, that had seemed to endorse sweeping congressional power to implement treaty promises.
But Chief Justice John G. Roberts, Jr., writing for himself and five other Justices, invoked the traditional practice of avoiding constitutional issues if not necessary to a decision, and chose to deal only with the question of whether Congress had meant to pass a law that was so nearly limitless that it would reach “a purely local crime” growing out of “romantic jealousy.”
‘The global need to prevent chemical warfare,” the Chief Justice wrote, “does not require the federal government to reach into the kitchen cupboard, or to treat a local assault with a chemical irritant as the deployment of a chemical weapon.   There is no reason to suppose that Congress — in implementing the Convention on Chemical Weapons — thought otherwise.”
Among other reasons that the majority felt driven to read the 1998 law narrowly was its view that, as applied to Carol Anne Bond’s case, the law meant a deep intrusion into the traditional authority of states to enforce criminal laws within their own jurisdictions.  The decision did not in any way seek to absolve her of criminal behavior, but stressed that this was a matter that state law could handle.