California Republicans swiftly moved to file a lawsuit against a controversial redistricting ballot measure pushed by Gov. Gavin Newsom (D-CA) after voters approved the measure during Tuesday’s off-year elections.

Republicans claim in a lawsuit that the new map that will be enacted as a result of Proposition 50, giving Democrats five more favorable congressional districts, is unconstitutional. The lawsuit was filed in the U.S. District Court for the Central District of California by the Dhillon Law Group on behalf of the California GOP. The lawsuit claims that the new maps illegally use voters’ race to draw new districts.