CULLMAN, Ala. — On a sofa in the hallway of his office here, Mitchell Williams, the pastor of First United Methodist Church, announced that he was going to break the law. He is not the only church leader making such a declaration these days.

Since June, when Gov. Robert Bentley, a Republican, signed an immigration enforcement law called the toughest in the country by critics and supporters alike, the opposition has been vocal and unceasing.

Thousands of protesters have marched. Anxious farmers and contractors have personally confronted their lawmakers. The American Civil Liberties Union and other civil rights groups have sued, and have been backed by a list of groups including teachers’ unions and 16 foreign countries. Several county sheriffs, who will have to enforce parts of the new law, have filed affidavits supporting the legal challenges.

On Aug. 1, the Justice Department joined the fray, contending, as in a similar suit in Arizona, that the state law pre-empts federal authority to administer and enforce immigration laws.