The American Civil Liberties Union has urged a federal court to block a South Carolina voter ID law from taking effect because of concerns that it would have a disproportionate effect on minority voters.

“South Carolina’s voter ID law is a prime example why the Voting Rights Act is necessary and relevant today,” said Nancy Abudu, senior staff attorney with the ACLU Voting Rights Project. “If it were not for the protections that the Voting Rights Act provides, South Carolina and many other states would enact discriminatory voting laws that make it harder for minorities to vote.”

The law, which was passed last spring by the South Carolina state legislature and signed by Gov. Nikki Haley (R), requires voters to present a government-issued photo ID before casting a ballot. Under the law, the Department of Motor Vehicles is required to issue free photo ID cards to voters.

Under Section 5 of the Voting Rights Act, the U.S. Department of Justice or a federal court is required to pre-clear laws affecting voters in jurisdictions with a history of voting discrimination, including South Carolina. The Justice Department blocked the law in December after finding over a third of the state’s minorities who are registered voters did not have the proper photo ID. South Carolina took the issue to court in February.

The ACLU filed a motion in the U.S. District Court for the District of Columbia in order to intervene in the case, South Carolina v. Holder.

The motion was filed on behalf of two African Americans who do not have an acceptable form of ID under the new law and the Family Unit, a non-profit group that helps people register to vote.

“Despite the lack of proof that voter impersonation is a problem in South Carolina, and despite evidence that African-Americans are less likely than whites to possess the forms of ID that the law requires, state officials have chosen to defend this unnecessary and unfair law,” said Victoria Middleton, executive director of the ACLU of South Carolina. “Our elected officials should make it easier for South Carolinians to exercise their right to vote, not put more barriers in their way.”