In today’s ruling in Bond v. United States, the Supreme Court was obviously right to reverse as federal overreaching the conviction of a woman who used certain chemicals to attack her husband’s paramour. This was a “purely local crime,” and the decision to prosecute Carol Anne Bond for it under a law that implements the international Chemical Weapons Convention was an abuse of federal power.

But 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. Bond was a case about the scope of the treaty power—can Congress do something pursuant to a treaty that it can’t otherwise do?—and yet the majority opinion avoided that discussion altogether in the name of a faux judicial minimalism. That’s not surprising given that its author is Chief Justice Roberts, who goes out of his way to avoid hard calls whenever possible. (Sometimes the practical result is still the right one, as here, sometimes it’s disastrously not, as in NFIB v. Sebelius, the Obamacare case, and sometimes even Roberts finds it impossible to avoid the Court’s constitutional duty, as in Citizens United and Shelby County.)

It was thus left to Justice Scalia, joined by Justices Thomas and Alito (in part), to do the hard work—to make those balls-and-strikes calls that Roberts promised at his confirmation hearing—and repudiate Missouri v. Holland, the 1920 case that’s been understood to mean that the federal government can indeed expand its own power by agreeing to do so with a foreign treaty partner. (Scalia’s opinion tracks Cato’s amicus brief closely, and cites my colleague Nicholas Quinn Rosenkranz’s groundbreaking work in this area.)

One other takeaway here is that the Obama administration has yet again lost unanimously at the Supreme Court, adding to its record number of goose eggs—particularly in cases involving preposterous assertions of federal power. Here Chief Justice Roberts provides the apt langiappe: “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.”