Last week, the Supreme Court finally decided a case, Carol Anne Bond v. United States, that the justices had been chewing over for seven months. George Will called it the “most momentous case” of this term, but unless you are a Court junkie, you probably never heard of it.

The case was important because conservative legal activists had seized upon it as a platform for exhuming, through constitutional reinterpretation, a long-dormant radical agenda. These activists saw the case as an opportunity to eviscerate the federal government’s capacity to enter into binding international agreements. But last Monday, Chief Justice John Roberts turned Will’s “momentous case” into a non-event. Writing for a majority that included Justice Anthony Kennedy and the Court’s four progressive justices, Roberts side-stepped his traditional ideological allies’ recipe for constitutional upheaval. Instead, Roberts narrowly construed the statute under challenge in the case to avoid ruling on the far-reaching constitutional theories they had propounded. Neo-isolationists on the right were deflated, internationalists relieved. But progressives, and for that matter, moderates and conservatives who value the federal government’s capacity to maintain its global leadership role, need to see this case as a wake-up call, and to fully take on board the lessons it teaches.

As the early twenty-first-century Republican Party has lurched rightward, a hobgoblin has resurfaced, rarely sighted since the 1950s, when fervent isolationism gripped the party. Congressional Republicans feared that liberal governments might use international treaties to ratchet up domestic human rights safeguards, or educational standards, or food safety requirements. The Tea Party has revived many of these fears—but this time around conservative activists have focused their strategy on the five-justice majority of the most conservative Supreme Court for at least the last three-quarters of a century. Accordingly, in the past several years, conservative and libertarian academics have come up with novel constitutional theories that would, if adopted by the Supreme Court, handily achieve their ends.

These scholars used the Bond case to argue that the Justice Department had stretched the federal treaty power to punish individual misconduct of no international significance and traditionally subject solely to state and local law. In 2007, the Department criminally charged, under a federal law implementing the 1993 international convention banning the use of chemical weapons, a woman who had taken toxic chemicals from the pharmaceutical lab where she worked, to inflict minor burns on her husband’s lover. Seizing on this prosecution—Solicitor General Donald Verrilli was obliged to acknowledge in oral argument before the Supreme Court that “whether or not Ms. Bond is prosecuted would [not] give rise to an international incident”—conservatives recruited their top Supreme Court advocate, Paul Clement, to take over Ms. Bond’s defense.

Clement, and more boldly, several amicus curiae (“friend of the court”) briefs filed by right-wing think tanks and advocates, proposed drastic limitations on the treaty power, functionally equivalent to restrictions originally proposed by mid-twentieth-century isolationists in the form of a constitutional amendment, known as the Bricker Amendment after its sponsor, Senator John W. Bricker of Ohio. The Bricker Amendment provided that Congress could only pass legislation to implement (i.e., ensure U.S. compliance with) an international treaty if the legislation was authorized by the “enumerated” powers assigned to Congress by the Constitution, such as the power to regulate commerce; if a treaty addressed matters not covered by those enumerated powers, Congress could not enforce it. President Eisenhower fiercely opposed the proposal because it would “shackle the federal government so that it is no longer sovereign in foreign affairs.” But congressional isolationists were bent on repudiating the bipartisan internationalism that had made possible victory in World War II and the postwar, U.S.-engineered framework of international institutions. They so dominated the Republican majorities in the Senate and House that only the parliamentary legerdemain of the Democrats’ newly elected Senate Minority Leader, Lyndon Baines Johnson, enabled the White House to defeat the isolationist proposal.