Ex parte Milligan, 71 U.S. (4 Wall.) 2 (1866), was a United States Supreme Court case that ruled that the application of military tribunals to citizens when civilian courts are still operating is unconstitutional. It was also controversial because it was one of the first cases after the end of the American Civil War.

Lambdin P. Milligan and four others were accused of planning to steal Union weapons and invade Union prisoner-of-war camps. Once the first prisoner of war camp was liberated, they planned to use the liberated soldiers to help fight against the Government of Indiana and free other camps of Confederate soldiers. They also planned to take over the state governments of Indiana, Ohio, and Michigan. When the plan leaked, they were charged, found guilty, and sentenced to hang by a military court in 1864. However, their execution was not set until May 1865, so they were able to argue the case after the Civil War ended.

The argument for the United States was delivered by Benjamin F. Butler, a Massachusetts lawyer and state legislator, and future Governor of Massachusetts.

John Peter Zenger (October 26, 1697 – July 28, 1746) was a German-American printer, publisher, editor and journalist in New York City. He was a defendant in a landmark legal case in American jurisprudence that determined that truth was a defense against charges of libel and "laid the foundation for American press freedom."

The "Penman of the Constitution", Gouverneur Morris, wrote this of the Zenger case: "The trial of Zenger in 1735 was the germ of American freedom, the morning star of that liberty which subsequently revolutionized America."

In the later part of 1733 John Peter Zenger began publishing a newspaper in New York to voice opposition to the onerous policies of newly appointed colonial governor William Cosby. Upon his arrival in New York, Cosby plunged into a rancorous quarrel with the Council of the colony over his salary. Unable to control the state's Supreme Court he removed Chief Justice Lewis Morris, replacing him with James DeLancey of the royal party. Supported by members of the popular party, Zenger's New-York Weekly Journal continued to publish articles critical of the royal governor. Finally, Cosby issued a proclamation condemning the newspaper's "divers scandalous, virulent, false and seditious reflections." On Sunday, November 17, 1734, Zenger was arrested and charged with seditious libel. After more than eight months in prison, Zenger went to trial defended by illustrious Philadelphia lawyer Andrew Hamilton. The case was now a cause célèbre with public interest at fever-pitch. Rebuffed repeatedly by Chief Justice DeLancey during the trial, Hamilton decided to plead his client's case directly to the jury. After the arguments for both sides were finished, the jury was retired, only to return in ten minutes with a verdict of not guilty.