The Supreme Court ruled in favor today of a woman who had been prosecuted for allegedly poisoning her husband's lover under a federal law aimed at deterring chemical weapons.

When Carol Anne Bond learned her husband was the father of her best friend's baby in 2006, she took matters into her own hands, according to prosecutors. Using her background as a microbiologist, she allegedly attempted to poison her friend, Myrlinda Haynes. Bond used a combination of chemicals that she stole from her boss and bought on the Internet.

Throughout the ordeal, Haynes' worst injury was a thumb burn.

Bond, however, was prosecuted under the Chemical Weapons Convention Implementation Act, a federal law that was passed to comply with a Chemical Weapons Convention treaty. The law forbids any person knowingly to "develop, produce, otherwise acquire" any chemical weapon.

Today a unanimous Supreme Court threw out the conviction.

Chief Justice John Roberts wrote that the law "does not cover the unremarkable local offense" at issue in the Bond case.

Roberts said that state laws would have been sufficient to prosecute Bond and that the "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. There is no reason to suppose that Congress-in implementing the Convention on Chemical Weapons-thought otherwise."

Roberts began his opinion with the background of the law that was passed to fulfill the United States' obligation under the Convention on Chemical Weapons.

He described the 1919 John Singer Sargent painting that captures the "horrors of chemical warfare " and said "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."

Roberts wrote the painting reflects the devastation that Sargent witnessed in the aftermath of the Second Battle of Arras during World War I and reiterated that the battle, like others , "led to an overwhelming consensus in the international community that toxic chemicals should never again be used as weapons against human beings."

But Roberts said the question in the Bond case is whether the law that implements the treaty also reaches a "purely local" crime. He described Bond's crime as "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.

"There is no reason to think the sovereign nations that ratified the Convention were interested in anything like Bond's common law assault," Roberts wrote.

Roberts criticized the government's reading of the law saying that the chemicals used in the Bond case were not the sort that an ordinary person would associate with instruments of chemical warfare.

"We are reluctant to ignore the ordinary meaning of 'chemical weapon' when doing so would transform a statute passed to implement the international Convention on Chemical Weapons into one that also makes it a federal offense to poison goldfish," he said.

Roberts closed the opinion by saying "there are no life-sized paintings of Bond's rival washing her thumb. And there are no apparent interests of the United States Congress or the community of nations in seeing Bond end up in federal prison, rather than dealt with (like virtually all other criminals in Pennsylvania) by the state."

Bond pleaded guilty in 2007 to two counts of using a chemical weapon and received a six year prison sentence. She was released from a federal prison in West Virginia in August 2012, and remains under court-ordered supervision, the Associated Press reported.

The chief justice was joined by Justices Anthony Kennedy, Ruth Bader Ginsburg, Stephen Breyer, Sonia Sotomayor and Elena Kagan. Justices Antonin Scalia, Clarence Thomas and Samuel Alito filed opinions concurring in the judgment.

The three justices agreed that Bond's conviction should be overturned, but said the case should have been decided on constitutional grounds.

Scalia criticized Roberts for failing to decide a long-simmering dispute on the limit of Congress' power to implement treaties.

Georgetown Law professor Nicholas Quinn Rosenkranz, who filed a brief in support of Bond, agrees with Scalia. "Scalia would have overruled court precedent and held that a treaty cannot increase the legislative power of Congress, and so Congress lacked the power to pass this provision of the law."