Federal judges struck down Wisconsin’s legislative map as illegally partisan, an unusual ruling that will require the Supreme Court to once again consider whether political gerrymandering violates the Constitution. It is a question the court has addressed in the past without resolution. In its last attempt, Justice Antonin Scalia, who died in February, wrote that it was impossible for courts to come up with a test to decide when partisan line-drawing goes so far as to violate the rights of those who don’t belong to the party in power. But the justices are divided, and they have not shut the door to the possibility that such violations could exist.