WASHINGTON (AP) — A unanimous Supreme Court ruled Monday that prosecutors may not rely on an international chemical weapons treaty to convict a woman who attacked her husband's mistress.

The justices threw out the conviction of Carol Anne Bond of Lansdale, Pa., who was prosecuted under a 1999 law based on the chemical weapons treaty. Bond served a six-year prison term after being convicted of using toxic chemicals that caused a thumb burn on a friend who had become her husband's lover.

Chief Justice John Roberts said Pennsylvania laws are sufficient to deal with the threats posed by a woman in a love triangle.

"In sum, the global need to prevent chemical warfare 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," Roberts said.

The case posed potentially significant questions about the federal government's power to make and enforce treaties. The justices resolved the case without reaching that issue, although Justices Samuel Alito, Antonin Scalia and Clarence Thomas said they would have.

Bond, unable to bear any children of her own, was excited for her best friend Myrlina Haynes when the woman announced her pregnancy. But later the excitement turned to pain when Bond found out that her husband of more than 14 years, Clifford Bond, was the one who had impregnated Haynes.

Vowing revenge, Bond, a laboratory technician, stole the chemical 10-chloro-10H phenoxarsine from the company where she worked and purchased potassium dichromate on Amazon.com. Both can be deadly if ingested or exposed to the skin at sufficiently high levels.

Bond spread the chemicals on Haynes' door handle and in the tailpipe of Haynes' car. Haynes, noticing the chemicals and suffering a minor burn, called the local police, who didn't investigate to her satisfaction. She then found some of the chemicals on her mailbox, and called the United States Postal Service, which videotaped Bond going back and forth between Haynes' car and the mailbox with the chemicals.

Postal inspectors arrested her.

But instead of turning the domestic dispute case over to state prosecutors, a federal grand jury indicted her on two counts of possessing and using a chemical weapon. The grand jury based the charges on a federal anti-terrorism law passed to fulfill the United States' international treaty obligations under the 1993 Convention on the Prohibition of the Development, Production, Stockpiling and use of Chemical Weapons and on Their Destruction.

Bond pleaded guilty,

The case is Bond v. U.S., 12-158.