Basse v. Brownsville 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 mandamus to a county court. The case arose when the plaintiff, Basse, sought to compel the county court to issue a writ of mandamus to the defendant, Brownsville, to compel him to pay a debt. The Supreme Court held that the state court did not have the authority to issue the writ of mandamus, as the county court was a separate court with its own jurisdiction. The Court reasoned that the state court could not interfere with the county court's jurisdiction, and thus the writ of mandamus was not valid. The Court also held that the state court could not issue a writ of mandamus to compel the county court to issue a writ of mandamus, as this would be an interference with the county court's jurisdiction. The Court concluded that the state court did not have the authority to issue the writ of mandamus, and thus the writ was invalid.

Justice Harlan delivered the dissenting opinion in Basse v. Brownsville, arguing that the majority's decision was contrary to established precedent and would lead to a dangerous expansion of federal power. He argued that Congress had no authority under Article I of the Constitution to pass legislation granting exclusive jurisdiction over certain areas within states without their consent, as it did with this case. Furthermore, he noted that if such an act were allowed then Congress could effectively override state laws by passing similar acts for any area within a state they chose. This would be an unconstitutional extension of congressional power and should not be permitted by the Court. Justice Harlan concluded his dissent by noting that while he sympathized with those affected by this particular dispute, allowing such an act would set a dangerous precedent which could have far-reaching implications on future cases involving Congressional powers versus State rights.