Although the Justice Department is an agency of the executive branch of the government, it has a natural association with the judicial branch. Many of the cases heard in the federal courts involve the national government in one capacity or another. Sometimes the government is sued; in other instances the government initiates the lawsuit. In either case, an attorney must represent the government. Most of the litigation involving the federal government is handled by the Justice Department, although a number of other government agencies have attorneys on their payrolls.

The Justice Department's Office of the Solicitor General is extremely important in cases argued before the Supreme Court. The department also has several legal divisions, each with a staff of specialized lawyers and headed by an assistant attorney general. The legal divisions supervise the handling of litigation by the U.S. attorneys, take cases to the courts of appeals, and aid the solicitor general's office in cases argued before the Supreme Court.