As a key battleground in this year’s presidential election, Ohio has already seen its share of voting-related litigation. The U.S. Court of Appeals for the Sixth Circuit has already weighed in with several rulings on the counting of provisional ballots and on expanded early voting hours.

But there is another important legal issue peculiar to Ohio that hasn’t gotten much attention so far, though it will be a significant factor should the state’s election tally spark litigation. Under a little-noticed provision of Ohio law, federal election results cannot be challenged in state court.

The provision is relatively new. Before 2006, legal challenges to the results of any statewide or federal race went to the state Supreme Court first under a statutory procedure. But early that year, Ohio legislators passed a law prohibiting federal election results from being contested under state law. Such challenges must now be brought under federal law.

What’s not clear is how that would work. “There is no federal statutory law that creates the same sort of election contest as under Ohio law,” says professor Steven Huefner of The Ohio State University’s Moritz College of Law. A plaintiff might, for example, bring an equal protection claim in federal court, Huefner says, though there does not appear to be a precedent for pursuing such a claim.

Huefner notes that both of the big federal election litigation battles the country has seen in recent years—Bush v. Gore in Florida in 2000, and the fight that dragged on after the 2008 election for a U.S. Senate seat in Minnesota between Norm Coleman and Al Franken, who ultimately prevailed—began in state court.

Ohio’s state court exclusion was adopted amid a sweeping overhaul of voting laws passed by Republican lawmakers in the wake of the fierce battle between President George W. Bush and John Kerry for the state’s 20 electoral votes in 2004. Citing a host of alleged problems with Ohio’s election procedures, Kerry supporters contested the vote tally in a case that the state Supreme Court summarily rejected. (As a result of the 2010 census, Ohio now has 18 electoral votes.)

S. Candice Hoke, an associate professor at Cleveland-Marshall College of Law, notes that “an extremely partisan vote” led to the bill’s passage. All but three Republicans in the state legislature voted for the law, and every Democrat lawmaker voted against it. The bill also included more stringent voter identification rules and restrictions on paid voter-registration drives. Hoke points out Ohio’s current secretary of state, Jon Husted—who oversees elections in the state—was the Republican House speaker when the law passed.

The state court exclusion has never been tested, so it’s hard to say how any potential federal litigation would play out, Hoke says. Along with a potential equal protection claim in federal court, voters could possibly bring a suit under the Help America Vote Act, the 2002 law that created minimum election administration standards. There is no guarantee, however, that a voter or candidate would have standing to bring a suit under the law, she says.

It’s also not clear whether the prohibition against bringing federal voting challenges in Ohio state courts would benefit Republicans in the end. The Ohio Supreme Court, which heard such challenges in the past, consists of six elected Republicans and one Democrat. Ohio’s federal judges, on the other hand, have ruled against Husted in most of the preelection challenges brought over the state’s voting laws and procedures. “This [provision] is not unambiguously good for Republicans,” says Professor Daniel Tokaji at Ohio State’s Moritz College of Law.

So far, legal fights over voting hours and provisional ballots have overshadowed Ohio’s state court exclusion. With so much riding on Ohio this year, that could change in the next couple of days. “At some point,” says Huefner, “when there is enough of a case to be made that something has gone wrong that affects the election outcome, people will sit up and take notice that state courts can’t consider this.”