The decision raises serious doubts about whether the law - and similar measures in at least 15 other states - can survive amid complaints that they violate free speech rights.
The high court said the Susan B. Anthony List does not have to wait until it is prosecuted under the law to claim its First Amendment rights have been infringed. The court did not directly rule on the constitutionality of the law, but the decision sends the case back to a lower court to consider the question.
Writing for the court, Justice Clarence Thomas said the existence of the law already has a chilling effect on political speech because people and interest groups have reason to believe their statements may be censured.
Both liberal and conservative groups have criticized the law, saying it stifles the wide-open debate crucial during elections, including negative speech that may sometimes twist the facts. Even Ohio attorney general Mike DeWine declined to defend the law in court, citing constitutional concerns. He sent his deputies to argue for the state instead.
The case began during the 2010 election when the Susan B. Anthony List, planned to put up billboards ads attacking then-Rep. Steve Driehaus. The ads accused Driehaus of supporting taxpayer-funded abortion because he supported President Barack Obama's new health care law. Driehaus, a Democrat who opposes abortion, claimed the ads misrepresented the true facts and therefore violated the false speech law.
After Driehaus filed a formal complaint, the billboard owner feared legal action and declined to post the ads. The Ohio Elections Commission found probable cause that the ads violated the law, but Driehaus later dropped the case after losing his re-election bid.
When the Susan B. Anthony List challenged the state law as unconstitutional, a federal judge said the group didn't have the right to sue because the case was withdrawn and it hadn't suffered actual harm. The 6th U.S. Circuit Court of Appeals in Cincinnati agreed.
In reversing the lower courts, the Supreme Court Thomas said the Susan B. Anthony List intends to make the same statements in future elections. That means the speech will remain prohibited under the Ohio false statement law.
"There is every reason to think that similar speech in the future will result in similar proceedings, notwithstanding SBA's belief in the truth of its allegations," Thomas said.
Thomas said the threat of commission proceedings is like arrest or prosecution in that it "may give rise to harm sufficient to justify pre-enforcement review.