On March 9, 1829, he resigned from the Senate to accept the position of Attorney General in the Cabinet of President Andrew Jackson. His first assignment was to prosecute former Treasury Fourth Auditor Tobias Watkins for embezzlement of public funds. Berrien secured a conviction at a high profile that same year. Later Berrien supported states' rights in the Nullification Crisis. In the case of the Negro Seamen Acts, he considered the acts to be appropriate exercises of the states' police powers, and beyond the reach of the federal government. He resigned from the office of Attorney General on June 22, 1831.