The Democratic candidate for a House seat in New York’s 26th congressional district in 2004 and 2006, Jack Davis, finally got what he was asking for when the Supreme Court struck down the Millionaire’s Amendment yesterday by a 5-4 ruling in Davis v. Federal Election Commission.

The amendment would have allowed raises in contribution limits for candidates when their opponents declare an intention to self-fund by more than $350,000. Although Mr. Davis spent more than $3 million of his own money for both races, he lost. Running again this year, Mr. Davis sought relief from the courts in being able to finance his own race without suffering regulatory disadvantage.

Yesterday, he got it.

Justice Alito wrote that the Millionaire’s Amendment penalized Mr. Davis’s right to spend money on his campaign. In Justice Alito’s judgment, the inability of candidates like Mr. Davis to exercise their First Amendment rights “produces fundraising advantages for opponents in the competitive context of electoral politics.”

By imposing additional costs on electoral spending, the Millionaire’s Amendment leads to less spending and less speech. And while congressmen would love to hear less speech from self-funders, the Court said that the Constitution frowns on their self-serving law.

In 1976, Congress imposed limits on campaign contributions by individuals and organizations. These restrictions were said to prevent corruption — one couldn’t give enough money to a candidate in order to buy a favor — or the appearance of corruption. The Supreme Court later decided that such limits could not apply to candidates who funded their own campaigns. After all, a self-funder can’t buy favors from himself.

As part of the 2002 Bipartisan Campaign Reform Act (McCain-Feingold’s formal name), however, Congress passed a “Millionaire’s Amendment,” which tried to “level the playing field” for opponents of self-funding candidates. The more a self-funder spent, the higher individual contributions his opponent could receive. And restrictions on coordinated spending of the opponent’s political party also evaporated. With loosened limits — a “get out of McCain-Feingold free” card — the opponent could ensure that the self-funder wasn’t allowed to “buy a seat” in Congress.

That’s not the whole story, of course. Need we tell you that an incumbent congressman’s worst fear is a millionaire challenger? Incumbents almost always have more money than their opponents and they also almost always win reelections, and naturally they prefer unfunded challengers and minimal competition. Hence the Millionaire’s Amendment.

In floor debates before McCain-Feingold passed, congressmen argued that the amendment was necessary to neutralize the financial advantages of wealthy self-funders, but thankfully, the Court has never accepted a “level playing field” rationale for political speech restrictions.

Some current examples suggest the wisdom of the Court’s rejection of “equal speech.” Al Franken became famous as a comedian and critic of the Bush administration. Should his celebrity — a formidable asset for his campaign — force television networks that play his material to provide his competitor in Minnesota’s senate race with equal airtime? And when newspapers endorse candidates, should government edict force other newspapers to endorse their opponents?

We rely on the judiciary to protect our rights, especially when Congress threatens them, and the courts’ job is particularly hard in cases involving political speech. Campaign finance reformers believe money is the root of all evil in politics, and that Congress should be in the business of stamping out this evil. But speaking out on politics — the very freedom the Founders most sought to protect in the First Amendment — demands raising and spending money.

While the Roberts Court appears determined to protect freedom of speech, both presidential candidates have been at least as enthusiastic for limits on campaign speech as Congress has. John McCain, of course, co-sponsored the law that enacted the Millionaire’s Amendment. And Barack Obama has spoken of the need for further campaign finance “reform,” while nonetheless opting out of the public financing system for the general election.

The Supreme Court has shown considerable courage in defending First Amendment rights. As it’s currently composed, the Court might even have struck down McCain-Feingold at its inception. The danger is far from over, but at last, the judiciary is living up to its obligation to protect free speech.

Mr. Samples is the director of the Center for Representative Government. Ilya Shapiro, who co-wrote this article, is a senior fellow in constitutional studies. Both are at the Cato Institute, which filed an amicus brief in the case.