The Fourteenth Amendment to the U.S. Constitution prohibits states from denying to any person “the equal protection of the laws.” Thus, on its face, the clause applies only to actions of the states or municipalities, and not the federal government. The Supreme Court, however, has repeatedly held that the rights of equal protection also apply to the federal government through the due process clause of the Fifth Amendment.
Equal protection guarantees that no person or group will be denied the protection under the law that is enjoyed by similar persons or groups. In other words, persons similarly situated must be similarly treated. It has been invoked in literally thousands of cases to protect against discrimination based on race, religion, nationality, gender and other classifications.