WASHINGTON (AP) — The Justice Department is suing Texas over a new state law that bans most abortions, arguing that it was enacted “in open defiance of the Constitution.”

The lawsuit, filed Thursday in federal court in Texas, asks a federal judge to declare that the law is invalid, “to enjoin its enforcement, and to protect the rights that Texas has violated.”

The Texas law, known as SB8, prohibits abortions once medical professionals can detect cardiac activity — usually around six weeks, before some women know they’re pregnant. Courts have blocked other states from imposing similar restrictions, but Texas’ law differs significantly because it leaves enforcement to private citizens through civil lawsuits instead of criminal prosecutors.

Pressure had been mounting on the Justice Department not only from the White House – President Joe Biden has said the law is “almost un-American” – but also from Democrats in Congress, who wanted Attorney General Merrick Garland to take action. Earlier this week, Garland vowed the Justice Department would step in to enforce a federal law known as the Freedom of Access to Clinic Entrances Act.

That law, commonly known as the FACE Act, normally prohibits physically obstructing access to abortion clinics by blocking entrances or threatening to use force to intimidate or interfere with someone. It also prohibits damaging property at abortion clinics and other reproductive health centers.