Five civil rights and civic engagement groups have filed suit against Georgia and its secretary of state for attempting to block registered voters from participating in a closely watched runoff election in Georgias 6th Congressional District.

On Thursday, the Lawyers Committee for Civil Rights Under Law filed a complaint in the federal district court in Atlanta, arguing that the state is violating the National Voter Registration Act. That law sets 30 days before a federal election as the earliest permissible deadline for voter registration.

Georgia complied with the provision for the special congressional election held this past Tuesday. But because no candidate won 50 percent of the vote, there will be a second election on June 20 a runoff between the top two finishers, Democrat Jon Ossoff and Republican Karen Handel.

Georgia election officials contend that the June runoff is simply a continuation of the special election this week, so they dont have to allow newly registered voters to participate. The registration deadline for Tuesdays election was March 20, and officials say anybody who registers after that day is not eligible to vote in the June runoff.

Ezra Rosenberg, co-director of the voting rights project at the Lawyers Committee, argues that under the federal law, Georgia cant set the registration deadline for the June 20 runoff any earlier than 30 days before that election that is, May 22.

The case is actually a very, very simple case, Rosenberg told reporters on a conference call Thursday. Federal law specifically defines elections as including runoff elections.

The National Voter Registration Act , passed in 1993, defines the word election based on the Federal Election Campaign Act. That 1971 statute defines an election as a general, special, primary, or runoff election .