Cammack v. Lewis was a United States Supreme Court case that dealt with the issue of whether a state court had the authority to issue a writ of habeas corpus to a prisoner held in federal custody. The case arose when the plaintiff, William Cammack, was arrested and held in federal custody in the state of Arkansas. Cammack sought a writ of habeas corpus from the state court, which was denied by the state court judge. Cammack then appealed to the Supreme Court, arguing that the state court had the authority to issue the writ. The Supreme Court ultimately ruled in favor of Cammack, holding that the state court did indeed have the authority to issue the writ of habeas corpus. The Court reasoned that the writ of habeas corpus was a fundamental right that could not be denied by any court, regardless of whether the court was state or federal. The Court also noted that the writ of habeas corpus was a necessary tool for protecting the rights of individuals who were held in federal custody. As such, the Court held that the state court had the authority to issue the writ of habeas corpus in this case.

In Cammack v. Lewis, the Supreme Court was asked to determine whether a state law that required certain individuals to pay an additional fee in order for them to be eligible for office violated the Fourteenth Amendment's Equal Protection Clause. The majority opinion held that it did not violate the clause because it applied equally across all classes of people and thus did not discriminate against any particular group or class of persons. However, Justice Field dissented from this decision on two grounds: first, he argued that while the law may have been facially neutral, its practical effect was discriminatory since only those who had sufficient funds were able to pay the extra fee; second, he argued that even if there was no discrimination in practice due to financial resources being equal among all classes of people, then still such a requirement would constitute an unconstitutional burden on one’s right to hold public office as guaranteed by Article IV Section 2 of the Constitution. In conclusion, Justice Field believed that regardless of how facially neutral a state law might appear at first glance – if its practical effects are discriminatory or impose an unconstitutional burden upon citizens seeking public office – then such laws should be struck down as violative of both constitutional principles and basic notions of fairness and equality under our system government.