Ex parte Dorr was a United States Supreme Court case that dealt with the issue of whether or not Thomas W. Dorr, who had been convicted for treason against Rhode Island in 1844, should be granted habeas corpus relief from his imprisonment. The court held that because he had been denied due process and trial by jury when he was initially arrested and tried, it would be unconstitutional to deny him habeas corpus relief. In its decision, the court stated that no state could suspend the writ of habeas corpus without violating Article I Section 9 of the Constitution which states "The Privilege of Habeas Corpus shall not be suspended unless when in Cases of Rebellion or Invasion." This ruling established an important precedent regarding civil liberties and constitutional rights as they relate to criminal proceedings.

In Ex Parte Dorr, the Supreme Court was asked to decide whether Rhode Island's constitution of 1842 violated the Constitution of the United States. The majority opinion held that it did not and upheld its validity. In his dissenting opinion, Justice McLean argued that Rhode Island had no authority to pass such a law without first obtaining consent from Congress as required by Article IV Section 4 of the U.S. Constitution which states "The United States shall guarantee to every State in this Union a Republican Form of Government". He further argued that since Congress had not given its approval for this new state constitution, it should be declared unconstitutional and void because it violated both federal law and fundamental principles of republican government enshrined in our nation’s founding documents. Furthermore, he noted that allowing states like Rhode Island to unilaterally change their constitutions would lead to chaos and undermine national unity by creating different laws between different states on matters concerning civil rights or other important issues affecting citizens across all jurisdictions within America’s borders