The U.S. Supreme Court, sidestepping a major constitutional test of Congress’ treaty powers, ruled unanimously last week that a vengeful act by a woman whose husband impregnated her best friend did not violate a federal law implementing a chemical-weapons treaty.

“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,” Chief Justice John Roberts Jr. wrote in reversing the conviction of Carol Anne Bond. “There is no reason to suppose that Congress—in implementing the Convention on Chemical Weapons—thought otherwise.”

After discovering that her best friend, Mylinda Haynes, was pregnant from an affair with Bond’s husband, Bond set out to get revenge by trying to poison her friend. She acquired toxic chemicals and, at various times, placed them on the Haynes’ car, mailbox and the doorknob of her home. Haynes subsequently suffered a burn to her thumb that she treated by rinsing it with water. After local police in Pennsylvania failed to help her, Haynes alerted postal authorities, who placed cameras in and around her home. Bond was arrested after being identified as the attacker.

Federal authorities prosecuted Bond under the statute implementing the Chemical Weapons Convention of 1993. The statute prohibits “knowing possession or use, for nonpeaceful purposes, of a chemical that can cause death, temporary incapacitation or permanent harm to humans.” The U.S. Court of Appeals for the Third Circuit upheld her conviction.

Her high court case, Bond v. U.S., had evolved as a potentially major test of Congress’ power to implement treaties negotiated by the executive branch. Bond, represented by Paul Clement of Bancroft, asked the high court whether Congress, in enacting a statute that applied to local criminal conduct, had exceeded its powers and invaded powers reserved to the states by the Tenth Amendment.

But citing the “well established principle” that the court normally will not decide a constitutional question if there is some other way to dispose of a case, the chief justice rested his opinion on the language and circumstances surrounding the enactment of the treaty and its implementing statute and on congressional intent.

“When used in the manner here, the chemicals in this case are not of the sort that an ordinary person would associate with instruments of chemical warfare,” Roberts wrote, adding that “no speaker in natural parlance would describe Bond’s feud-driven act of spreading irritating chemicals on Haynes’ door knob and mailbox as ‘combat.’ Nor do the other circumstances of Bond’s offense—an act of revenge born of romantic jealousy, meant to cause discomfort, that produced nothing more than a minor thumb burn—suggest that a chemical weapon was deployed in Norristown, Pennsylvania.”

The federal government’s reading of the statute, he said, was so broad that “any parent would be guilty of a serious federal offense—possession of a chemical weapon—when, exasperated by the children’s repeated failure to clean the goldfish tank, he considers poisoning the fish with a few drops of vinegar. 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.”

Although the decision was unanimous in its result, it revealed fault lines within the court, with three justices saying they would have reached the constitutional question and limited the government’s treaty power.

“Today, the court shirks its job and performs Congress,’ Justice Antonin Scalia wrote in a concurrence. “As sweeping and unsettling as the Chemical Weapons Convention Implementation Act of 1993 may be, it is clear beyond doubt that it covers what Bond did; and we have no authority to amend it. So we are forced to decide—there is no way around it—whether the act’s application to what Bond did was constitutional. I would hold that it was not.”

Scalia said he would have overruled a 1920 high court decision at the core of the constitutional issue: Missouri v. Holland, which held that although “the great body of private relations usually fall within the control of the state, a treaty may override its power.”

Justice Clarence Thomas, joined by Scalia and Justice Samuel Alito, wrote that the court, in an appropriate case, should address the scope of the treaty power “as it was originally understood.” Tracing its drafting history and court precedents, he said the power must relate only to intercourse with other nations.

Alito, agreeing with that limit, wrote in his own concurrence that “insofar as the [chemical-weapons] convention may be read to obligate the United States to enact domestic legislation criminalizing conduct of the sort at issue in this case, which typically is the sort of conduct regulated by the states, the convention exceeds the scope of the treaty power.”

Ilya Shapiro of the Cato Institute, an amicus party supporting Bond, accused Roberts of “faux judicial minimalism” for avoiding the constitutional question. “In deciding the case so narrowly, creatively reinterpreting an expansive federal statute instead of reaching the constitutional issue at the heart of this bizarre case, the court’s majority abdicated its duty to check the other branches of government,” he said.

However, Elizabeth Wydra of the Constitutional Accountability Center applauded the high court ruling, saying, “The court today refused to accept the invitation of conservatives, including Tea Party U.S. Senator Ted Cruz and Justice Scalia himself, to gut the constitutional power that gives the federal government authority to enact appropriate legislation to implement validly enacted treaties.” •