Deputy U.S. marshals assigned to guard Supreme Court justices last year were directed to try not to make arrests, according to documents a U.S. senator revealed Tuesday, contradicting Attorney General Merrick Garland’s assurances to Congress. Sen. Katie Britt, Alabama Republican, confronted Mr. Garland with the training package used for the marshals deployed to protect justices. It said arrests were “not” to be a priority. Mr. Garland told senators earlier this month that his prosecutors couldn’t bring cases unless the marshals made arrests, and the marshals on the scene didn’t think there was a reason to do that. Ms. Britt...