When is a movie not just a movie? According to the Federal Election Commission, when the film's villain isn't a terrorist or a drug dealer but a candidate for president. The agency decided that the producers of a 90-minute documentary critical of Hillary Rodham Clinton -- which they hoped to offer "on demand" to interested cable TV viewers -- had to abide by rules governing "electioneering communications," including a prohibition on advertising close to a primary or general election.

Fortunately, several justices of the Supreme Court indicated at oral arguments Tuesday that they would consider overturning the FEC's interpretation of a provision of the 2002 McCain-Feingold campaign finance law. They seemed receptive to an argument by Theodore B. Olson, the lawyer for the group Citizens United, that subjecting "Hillary: The Movie" to government regulation would threaten the "robust, uninhibited debate about a subject of intense political interest that the 1st Amendment is there to guarantee." Olson received some inadvertent aid from a lawyer for the Obama administration. Deputy Solicitor General Malcolm Stewart said it would be constitutional for the government to ban the preelection release not just of a film but of a book, "if the book contained the functional equivalent of express advocacy."

The restrictions on electioneering communications funded by unions or corporations were a well-intentioned add-on to McCain-Feingold. Congress had in mind phony issue ads, which criticized or praised a candidate without expressly urging his victory or defeat. Actually, the law went further, defining electioneering communications as any ad that mentioned a candidate in a forthcoming election.

In 2007, the Supreme Court properly overruled the FEC by holding that the antiabortion group Wisconsin Right to Life had a 1st Amendment right to air an ad urging the state's two Democratic senators -- only one of whom was up for reelection -- to allow confirmation votes on President Bush's judicial nominees.

Like the anti-Clinton Citizens United, Wisconsin Right to Life was a nonprofit organization that received some corporate funding. But it's hard to see how the 1st Amendment can tolerate the muzzling of any corporations that want to comment on an election. This newspaper, which reserves the right to endorse or criticize a candidate right up to election day, is owned by a corporation. So are most book publishers. Whatever the political or artistic merits of "Hillary: The Movie," the claim that it can be suppressed by the government deserves a thumbs-down from the court.