North Carolina judges who ruled the state’s legislative district maps were drawn to unconstitutionally favor Republicans are hiring a familiar expert to review how state lawmakers fix the problem.

The three-judge Superior Court panel on Friday appointed Stanford University law professor Nathaniel Persily to check the state General Assembly’s revisions. He may also redraw legislative districts himself if the judges decide legislators didn’t follow guidelines the court outlined earlier this month.

Persily served as a special master to a federal court panel that ruled in 2016 that more than two dozen of North Carolina’s 170 legislative districts approved in 2011 were illegal racial gerrymanders. The maps were revised by legislators in 2017, but the state judges ruled those districts were political gerrymanders.

Legislators have until Wednesday to complete their remedial maps.