Established in the case of Marbury v. Madison, the strict scrutiny test is applied by the United States court system in determining whether a government action infringes on the fundamental rights of the people.
In order to satisfy strict scrutiny, a law must be neither vague nor substantially over- or underinclusive. It must further an overriding state interest, yet be drawn with narrow specificity to avoid any unnecessary intrusion on First Amendment rights. Under the strict scrutiny test, a law is presumed to be infringing on the rights of the people unless the government can prove otherwise.
Strict scrutiny does not apply to all government laws, only those involving what the court considers to be a fundamental right of the people, such as those specifically enumerated in the Bill of Rights.