The US Supreme Court ruled Wednesday that a Republican congressman may bring suit to challenge an Illinois mail-in ballot law.

Chief Justice John Roberts wrote the 7-2 majority decision, which confirmed that Congressman Michael Bost had standing to continue his lawsuit in federal court, writing:

Candidates have a concrete and particularized interest in the rules that govern the counting of votes in their elections, regardless whether those rules harm their electoral prospects or increase the cost of their campaigns. Their interest extends to the integrity of the election—and the democratic process by which they earn or lose the support of the people they seek to represent.

Bost sued in 2022, claiming that the Illinois law infringed on a federal law, 2 U.S. Code § 7, that sets a uniform day for federal elections. In its opinion, the court did not consider whether his challenge had any legal merit.

Bost appealed to the Supreme Court after lower courts had held that he did not meet the threshold of demonstrating a “concrete and particularized” injury tied to the challenged law. However, Roberts disagreed lower court holdings, noting that counting unlawful votes or failing to count lawful votes erodes public confidence that the results of the elections reflected true democracy.

“When public confidence in the election results falters, public confidence in the elected representative follows. To the representative, that loss of legitimacy—or its diminution—is a concrete harm. ‘[R]eputational harms,’ as a general matter, are classic Article III injuries,” Roberts wrote.

Dissenting Justice Ketanji Brown Jackson worried the decision may lead to increased challenges from candidates following elections, writing:

Alarmingly, today’s ruling… opens the floodgates to exactly the type of troubling election-related litigation the Court purportedly wants to avoid… Under the Court’s new harm-free candidate-standing rule, an electoral candidate who loses in a landslide can apparently still file a disruptive legal action in federal court after the election is over… [T]he court now complicates and destabilizes both our standing law and America’s electoral processes.

Justice Amy Coney Barrett concurred with the majority but said she would have taken a more limited approach, holding that Bost had standing to continue his lawsuit because of the money his campaign had spent.

“This is a critically important step forward in the fight for election integrity and fair elections,” Bost said in a statement, adding that he would continue to pursue his case as “he navigate[s] the next stages of the legal process.”