District of Columbia v. McBlair is a United States Supreme Court case that was decided in 1887. The case involved a dispute between the District of Columbia and a man named McBlair over a piece of property. McBlair had purchased the property from the District of Columbia in 1883, but the District later attempted to reclaim the property, claiming that the sale was invalid. The Supreme Court ultimately sided with McBlair, ruling that the District of Columbia had no right to reclaim the property. The Court held that the District had no authority to sell the property in the first place, as it was not authorized to do so by Congress. The Court also held that the District was not entitled to reclaim the property, as it had not taken any steps to do so within the time period prescribed by law. The Court's decision in this case established that the District of Columbia was not authorized to sell property without the approval of Congress, and that it could not reclaim property that had been sold without its approval. This decision has been cited in numerous subsequent cases involving the District of Columbia's authority to sell property.

In District of Columbia v. McBlair, the Supreme Court was tasked with determining whether a tax imposed by Congress on certain real estate transactions in Washington D.C., which had been declared unconstitutional by the Circuit Court for the District of Columbia, could be enforced against parties who had already paid it under protest and sought to recover their money back from the government. The majority opinion held that since Congress has exclusive authority over taxation within its jurisdiction, any taxes imposed are valid unless they violate some other law or constitutional provision; thus, this particular tax was not invalidated as unconstitutional and therefore could still be enforced despite having been previously struck down in court. Justice Field dissented from this ruling because he believed that when a court declares something to be unconstitutional it should no longer have legal effect regardless of congressional power; if such were not true then individuals would never know what laws were actually binding upon them due to constantly changing judicial decisions. He argued further that allowing an unconstitutionally enacted law to remain enforceable would lead to chaos and confusion among citizens trying to comply with ever-shifting regulations without knowing which ones are truly valid or not.