U.S. Supreme Court justices expressed frustration with partisan gerrymandering on Wednesday as they heard arguments in a case challenging Maryland’s 6th Congressional District.

The case, which alleges a Democratic gerrymander in Maryland at the same time justices are considering the constitutionality of an alleged Republican gerrymander in Wisconsin, has some legal experts wondering whether the justices might be on the verge of establishing a standard that would allow judicial intervention in partisan gerrymandering cases for the first time in the court’s history.

The 6th District challenge was brought by seven Maryland residents, including three from Frederick County, who argue that the district — which includes southwestern parts of Frederick County and the city of Frederick — was unconstitutionally gerrymandered to favor Democrats and punish Republicans during the reapportionment process after the 2010 census.

The justices heard arguments in the Wisconsin political gerrymandering case in October, but have not yet released an opinion.

The Maryland and Wisconsin cases both focus on unconstitutional partisan gerrymandering, but there are some important differences. The Maryland case challenges the redrawing of a single federal district to favor Democrats, while the Wisconsin case is based on the statewide redrawing of Wisconsin State Assembly districts to favor Republicans.

The two cases also allege different violations of voters’ rights: The Maryland case claims retaliation against Republican voters under a First Amendment framework, while the Wisconsin plaintiffs are alleging a violation of the equal protection clause under the 14th Amendment.