In a 7–2 decision today, the Supreme Court struck down Minnesota’s blanket ban on wearing anything with a political insignia at a polling place. Chief Justice Roberts’s opinion agreed with many parts of Cato’s brief, particularly regarding the inherent unworkability of such a broad ban on political speech. The decision is a small but important victory for free speech.

In highlighting the unpredictability of the what counts as “political,” Chief Justice Roberts’s opinion cites one moment from oral argument that Supreme Court observers found particularly telling. When asked by Justice Alito whether the law would ban a shirt with the text of the Second Amendment, Daniel Rogan, counsel for Minnesota, said “I think that that could be viewed as political.” Alito then immediately asked whether the same would be true of a shirt with the text of the First Amendment. Observers in the courtroom laughed, and Rogan said “no your honor, I don’t think the First Amendment,” only to be interrupted by the Chief Justice, “No what, that it would be covered or wouldn’t be allowed?,” Roberts asked. “It would be allowed,” replied Rogan, but the Chief Justice seemed surprised, “it would be?,” he asked.

There’s a saying in Supreme Court practice that a case can’t be won at oral argument, but it can be lost. While Minnesota had a tough law to defend, but that exchange underscored the arbitrariness of the law. At a Cato forum in February, before the case was argued, I had a similar exchange with Ginger Anders of Munger, Tolles, and Olson, LLC when I asked her whether a Gerald Ford or a Ronald Reagan shirt would be banned. No to Ford, she said, but yes to Reagan.

So did Minnesota lose the case at oral argument? Roberts’s opinion goes almost out of its way to explain that bans on political expression in polling places are often valid, if not desirable:

Casting a vote is a weighty civic act, akin to a jury’s return of a verdict, or a representative’s vote on a piece of legislation. It is a time for choosing, not campaigning. The State may reasonably decide that the interior of the polling place should reflect that distinction.

From this language, it would seem that Roberts is writing to uphold the law. But “the State must draw a reasonable line,” he goes on to write, and “the unmoored use of the term ‘political’ in the Minnesota law, combined with haphazard interpretations the State has provided in official guidance and representations to this Court” mean the law should be struck down.

Every state and the District of Columbia have laws that prohibit certain types of speech around polling places on election day. If a state’s law provides specific enough standards for prohibited speech, then today’s decision won’t affect it. Those that let election judges make arbitrary distinctions, however, will likely be struck down.