Wells v. McGregor 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 a prisoner, William Wells, was held in federal custody in the state of Ohio. Wells sought a writ of habeas corpus from the state court, which was denied by the federal court. The Supreme Court ultimately held that the state court did not have the authority to issue a writ of habeas corpus to a prisoner held in federal custody. The Court reasoned that the writ of habeas corpus was a federal prerogative and that the state court did not have the authority to interfere with the federal court's decision. The Court also noted that the writ of habeas corpus was a fundamental right and that the state court should not be allowed to interfere with the federal court's decision. The Court's decision in Wells v. McGregor established the principle that state courts do not have the authority to issue a writ of habeas corpus to a prisoner held in federal custody.

In the case of Wells v. McGregor, Justice Field delivered a dissenting opinion in which he argued that the majority's decision was contrary to established precedent and would lead to an unjust result. He noted that prior decisions had held that when a party has been wrongfully deprived of their property, they are entitled to recover damages for its value at the time it was taken from them. In this case, however, the majority found that since there were no specific terms as to how much money should be paid for use of the land in question, then no compensation could be awarded even though McGregor had used it without permission or payment for several years. Justice Field disagreed with this conclusion and argued instead that under existing law Wells should have been allowed to recover damages based on what his property was worth at the time it was taken from him by McGregor.