The American Civil Liberties Union, taking a tougher stance on armed protests, will no longer defend hate groups seeking to march with firearms, the group’s executive director said.

Following clashes over the weekend in Charlottesville, Va., the civil-rights group also will screen clients more closely for the potential of violence at their rallies, said Anthony Romero, who has been the ACLU’s executive director since 2001.

The ACLU’s Virginia branch defended the right of white nationalists, neo-Nazis and other groups under the banner “Unite the Right” to protest the removal of a statue of Confederate Gen. Robert E. Lee from a Charlottesville park.

“The events of Charlottesville require any judge, any police chief and any legal group to look at the facts of any white-supremacy protests with a much finer comb,” said Mr. Romero.

The revised policy marries the 97-year-old civil-rights group’s First Amendment work with the organization’s stance on firearms, which aligns with many municipalities and states that bar protesters from carrying weapons.