On April 20, several voting rights groups sued Georgia, over the state’s March 20 deadline to register to vote in the special run-off election for U.S. House, sixth district. That run-off is set for June 20, but the deadline for registering to vote was March 21. Georgia State Conference of the NAACP v Kemp, n.d., 1:17cv-1397.
Federal law requires states to let people register to vote as late as 30 days before any federal election. Here is the Complaint. Thanks to Rick Hasen for the link.