"Minnesota’s political apparel ban violates the Free Speech Clause of the First Amendment."

That's the new Supreme Court case this morning, Minnesota Voters Alliance v. Mansky.

The Chief Justice writes the opinion and there's a dissent from Sotomayor (joined only by Breyer).

From the majority opinion:

[T]he ban applies only in a specific location: the interior of a polling place. It therefore implicates our “‘forum based’ approach for assessing restrictions that the government seeks to place on the use of its property.”...  This Court employs a distinct standard of review to assess speech restrictions in nonpublic forums.... A polling place in Minnesota qualifies as a nonpublic forum. It is, at least on Election Day, government-controlled property set aside for the sole purpose of voting....

We therefore evaluate MVA’s First Amendment challenge under the nonpublic forum standard. The text of the apparel ban makes no distinction based on the speaker’s political persuasion, so MVA does not claim that the ban discriminates on the basis of viewpoint on its face. The question accordingly is whether Minnesota’s ban on political apparel is “reasonable in light of the purpose served by the forum”: voting...

[W]e see no basis for rejecting Minnesota’s determination that some forms of advocacy should be excluded from the polling place, to set it aside as “an island of calm in which voters can peacefully contemplate their choices.”...

[I]]n light of the special purpose of the polling place itself, Minnesota may choose to prohibit certain apparel there because of the message it conveys, so that voters may focus on the important decisions immediately at hand. But the State must draw a reasonable line. Although there is no requirement of narrow tailoring in a nonpublic forum, the State must be able to articulate some sensible basis for distinguishing what may come in from what must stay out..... Here, 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, cause Minnesota’s restriction to fail even this forgiving test.

Again, the statute prohibits wearing a “political badge, political button, or other political insignia.” It does not define the term “political.” And the word can be expansive. It can encompass anything “of or relating to government, a government, or the conduct of governmental affairs,” Webster’s Third New International Dictionary 1755 (2002), or anything “[o]f, relating to, or dealing with the structure or affairs of government, politics, or the state,” American Heritage Dictionary 1401 (3d ed. 1996). Under a literal reading of those definitions, a button or T-shirt merely imploring others to “Vote!” could qualify. The State argues that the apparel ban should not be read so broadly. According to the State, the statute does not prohibit “any conceivably ‘political’ message” or cover “all ‘political’ speech, broadly construed.” Brief for Respondents 21, 23....

We do not doubt that the vast majority of election judges strive to enforce the statute in an evenhanded manner, nor that some degree of discretion in this setting is necessary. But that discretion must be guided by objective, workable standards. Without them, an election judge’s own politics may shape his views on what counts as “political.” And if voters experience or witness episodes of unfair or inconsistent enforcement of the ban, the State’s interest in maintaining a polling place free of distraction and disruption would be undermined by the very measure intended to further it....

[I]f a State wishes to set its polling places apart as areas free of partisan discord, it must employ a more discernible approach than the one Minnesota has offered here.

The Sotomayor opinion says that the state supreme court should have been given the opportunity to interpret the state statute and perhaps to give it a narrow enough meaning that word, "political," to avoid the question of federal constitutional law. Sotomayor notes that the statute has been around for more than a century, and this is the first time it's been challenged, so that indicates that the state hasn't been abusing its power and should therefore enjoy the respect of its courts getting the chance to interpret its own law. This process is called "certification." Sotomayor comes out on the federalism side: certification would "save time, energy, and resources and helps build a cooperative judicial federalism."

The majority addresses the federalism angle in a footnote:

Minnesota’s request for certification comes very late in the day: This litigation had been ongoing in the federal courts for over seven years before the State made its certification request in its merits brief before this Court...  And the State has not offered sufficient reason to believe that certification would obviate the need to address the constitutional question. Our analysis today reflects the State’s proffered interpretation; nothing in that analysis would change if the State’s interpretation were also adopted by the Minnesota Supreme Court. Nor has the State (or the dissent) suggested a viable alternative construction that the Minnesota Supreme Court might adopt instead.