In February of 2003, Hessam Ghane, an unemployed chemist, sat alone in his apartment in Independence, Missouri, grappling with the familiar clutch of depression. He called a crisis hotline and told the counselor who answered that he was considering suicide. After he hung up, two police officers arrived at his door. Ghane asked to be taken to a hospital with a psychiatric unit. The officers drove him to a nearby medical center in Kansas, where an emergency-room assistant asked Ghane if he had a way to take his life. Ghane admitted that he had a stolen jar of potassium cyanide for that purpose, but he didn’t want to surrender it. “I don’t want to give it up, because I might use it later,” he recalled telling the assistant.

Three months later, federal prosecutors charged Ghane with violating the federal law that codifies the Chemical Weapons Convention, the global disarmament treaty that the United States ratified in 1997. The convention, which built on earlier, weaker pacts, was intended to eradicate chemical weapons worldwide and is now being enforced in Syria. The signatory nations—there are a hundred and ninety of them—must adopt domestic laws to implement and enforce the treaty within their own borders. Ghane’s cyanide was a chemical weapon, the prosecutors claimed, and possessing it for a non-peaceful purpose—even if his purpose was only to harm himself—was illegal under the law. In December, 2010, after Ghane had spent almost eight years in pre-trial detention facilities, a jury convicted him. He was sentenced to ninety-seven months in federal prison—nearly the amount of time that he had already spent behind bars.

Ghane, who goes by “Sam,” had an unwelcome reminder of his case last week when the U.S. Supreme Court unanimously reversed the conviction of Carol Anne Bond, who had been prosecuted under the same law. Her case, in which she tried to use chemicals to harm her husband’s paramour, became a cause célèbre among some libertarian constitutional scholars as an example of overreaching treaty power. In the long-awaited ruling, the justices found that Bond’s crime was a simple assault that should have been handled by local law enforcement, and that her prosecution under the Chemical Weapons Convention was a misapplication of the law. “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 wrote in the majority opinion.

Those words have an ironic, albeit unintentional, double meaning in the context of Ghane’s case, because he kept the jar of the potassium cyanide in a bag under his kitchen sink. Ghane had hoped that the ruling would vindicate him. Instead, the majority ruling that tossed out Bond’s conviction specifically cited Ghane’s case as an example of a justified prosecution under the law, lumping him in with white supremacists who tried to get their hands on explosives and chemical weapons, and another man who released a chlorine gas cloud in a residential neighborhood.

Ghane has long insisted that he only kept the chemical for the purpose of killing himself. Even before the ruling, he felt deeply aggrieved that his conviction had pushed him into the ranks of the infamous few accused of hoarding and using chemical weapons, such as Bashar al-Assad. “It’s a joke to me,” Ghane told me over Skype from his lawyer’s office several months ago. “But what can I do? I’m one person, the bottom of the ladder.”

Ghane is among only a handful of domestic prosecutions since Congress passed the chemical-weapons statute in 1998. In one case, in Albany, New York, a man sprinkled mercury around a hospital with which he had a billing dispute. In Tucson, Arizona, a man released a chlorine gas cloud at a former customer’s home. A neo-Nazi in Tennessee was convicted for trying to obtain nerve agents from a military arsenal in Arkansas. Ghane’s case—though its circumstances are unusual—probably would have remained nothing more than a strange footnote in the history of chemical weapons disarmament but for the Bond case.

Bond gained notoriety in part because of the lurid details of the case—a jilted wife, a sordid affair, an out-of-wedlock child—but also because some conservative legal scholars believed that the domestic implementation law should have been struck down on constitutional grounds. That argument, notably made by Senator Ted Cruz, a Republican from Texas, was that the implementation law created a new, unconstitutional federal power. If the court took that position, many supporters of the law warned, other treaty laws could have been challenged on the same grounds. But that didn’t happen; instead the six-justice majority essentially sidestepped the constitutional question, ruling that Congress never intended the law to apply to “a purely local matter.”

The prosecutor’s case against Bond, as in Ghane’s, centered on the convention’s ban on using chemical weapons and their toxic components for anything other than “peaceful purposes.” The convention and the statute that implements it in the U.S. intentionally make no distinction between stockpiling warheads full of sarin and hoarding a stolen jar of chemicals. The framers of the convention deliberately made the pact as broad and as strict as possible, to stamp out even the most tentative first steps toward gathering precursor chemicals for weapons.

Barry Kellman, the director of the International Weapons Control Center at the DePaul University College of Law, told me that even before the U.S. ratified the convention, international-law experts considered the possibility that minor cases could arise because of the convention’s strict edicts against possessing toxic chemicals. In the nineties, he headed a group of legal experts who wrote a manual on implementing the treaty. Kellman said that the group wondered if the treaty’s provisions might result in prosecutions for minor infractions. They even discussed a hypothetical scenario—a woman serving poisoned pasta to her husband. In the end, the group dismissed that possibility, assuming that prosecutors would not pursue such cases. Kellman remains adamant that the law needs to be as strict as possible to be effective, but said that it wasn’t intended for cases like Bond’s or Ghane’s. Prosecuting such cases is a “distraction” from the real purpose of the law, which is pursuing offenders like Assad, Kellman told me.

“Nobody thought that it would arise,” Kellman said. “We were all talking about something that we didn’t think was going to happen.”

Whether it is peaceful to contemplate using toxic chemicals for suicide is a macabre ethical and philosophical question. Its legality under the convention, though, is not in doubt, at least in the eyes of federal prosecutors. Ghane’s problems had begun long before he arrived at the hospital in Kansas. Born in Iran, he left the country in the nineteen-seventies to seek better job prospects in the United States. He earned a Ph.D. in chemistry from Louisiana State University and became a U.S. citizen. After Ghane moved to Missouri, in 1992, to take a job with the U.S. Army Corps of Engineers, the corps fired him less than a year later. He performed poorly at work, his superiors claimed, and he had made threats that his then-girlfriend had reported. Ghane accused the corps of discrimination, and filed a lawsuit that a judge dismissed in 1997. As part of numerous hospital admissions for depression and thoughts of suicide, doctors noted his paranoid delusions about government persecution. After he ranted during one hospitalization about the judge who had thrown out his employment lawsuit, the F.B.I. questioned him. Around 2000, Ghane stole the potassium cyanide from a college where he had taught chemistry; he was worried, he testified in his trial, that his depression might become too much to bear..