Illegal voting maps were used in some states in 2022. This legal idea allowed them

The U.S. Supreme Court has used a vague legal idea known as the "Purcell principle" to justify delaying the redrawing of voting maps, which has forced some elections to use voting districts that lower courts found to be illegally drawn. (Mariam Zuhaib/AP)

A closely watched U.S. Supreme Court ruling last month confirmed that Alabama voters cast ballots in illegally drawn voting districts for Congress in the 2022 elections.

There's an obscure legal idea behind why the court allowed it to happen. It's known as the "Purcell principle."