And there are allegations that the state's decision could be aimed at "suppressing the black vote," local media reports say. 

Tennessee's voting rights policy was toughened last year to require that people convicted of a crime to have their gun rights restored in order to vote in ballots, including this year's presidential election. Felons are banned from buying or carrying firearms after they have served their prison terms. 

But it is not clear how convicted criminals should go about restoring their gun rights, due to confusion over what paperwork is required, which state officials sign the documents and how to go about an appeal if an application is denied – or if an appeal is even possible, say rights groups. 

Washington-based advocacy group the Campaign Legal Center has taken legal action over Tennessee's decision to stop people from voting and is suing the state in federal court. Blair Bowie, director of the center's Restore Your Vote program said Tennessee officials were not interpreting the law the correct way. 

Bowie told The Associated Press: "Despite the Tennessee legislature's clear intent to create meaningful pathways for voting rights restoration, the Elections Division, with help from the Attorney General's office, continues to twist the law into tortured knots to prevent the 475,000 Tennesseans, including over 20 percent of voting age Black Tennesseans, with past felony convictions from voting."

The move is estimated to affect 475,000 Tennesseans and has been condemned by rights groups for violating Americans' right to vote. Black Americans and Latinos are particularly affected, they say.