According to a report out today from The Washington Post, a major blow to the practice of redistricting, also known as gerrymandering, is materializing in courts around the country.

The practice of redistricting has been one of the Republican Party’s most effective tools for remaining in power. Every 10 years, states redraw their voting maps so that their election districts reflect population changes. This means that a district that has grown more ethnically diverse, for example, can be redrawn so that all of the African-American voters, who tend to vote Democratic, are moved into an already Democratic district, and Republicans get to stay in power quite literally against the will of the public. While both parties participate in the practice, most state legislatures are controlled, thanks to gerrymandering, by Republicans.

In 2010, Republican-led state legislatures embarked on a massive effort to redraw state districts around the country at the expense of minority and Democratic voters. A memo from the Republican State Leadership Committee explained the move:

Drawing new district lines in states with the most redistricting activity presented [Republicans] the opportunity to solidify conservative policymaking at the state level and maintain a Republican stronghold in the US House of Representatives for the next decade.

Now, a series of lawsuits threatens the practice for both parties. As The Post reported, “On Friday, a federal court ordered Wisconsin legislatures to redraw their state House legislative districts after finding in November that the districts were unconstitutionally partisan.”

That ruling marked the first time in more than 10 years that a court ordered a state to redraw legislative maps because they favored a particular party.

The Post also reported that in North Carolina, lawmakers are waiting on a decision from the Supreme Court that could end up forcing the state to redraw districts as well as hold special elections for 28 of its state legislative districts. Last summer, a federal court found that North Carolina Republican redistricting was unconstitutional because it was influenced by race.

The next time legislators will redraw districts nationwide is after the 2020 Census. With the current political climate, it will surely receive a great deal of scrutiny from the courts.

Correction:This article has been updated to correctly attribute news sources.