Hahn v. United States was a United States Supreme Court case that addressed the issue of whether a patentee could assign a patent to a third party without the consent of the patentee's assignor. The case involved a dispute between the patentee, Hahn, and the United States government. Hahn had assigned a patent to a third party without the consent of the patentee's assignor, the United States government. The government argued that the assignment was invalid because it had not given its consent. The Supreme Court held that the assignment was valid. The Court reasoned that the patentee had the right to assign the patent to a third party without the consent of the assignor. The Court noted that the patentee had the right to assign the patent to a third party, and that the assignor had no right to interfere with the assignment. The Court also noted that the patentee had the right to assign the patent to a third party without the consent of the assignor, and that the assignor had no right to interfere with the assignment. In conclusion, the Supreme Court held that the assignment of the patent to a third party was valid, and that the assignor had no right to interfere with the assignment. The Court noted that the patentee had the right to assign the patent to a third party without the consent of the assignor, and that the assignor had no right to interfere with the assignment.

Justice Field delivered the dissenting opinion in Hahn v. United States, arguing that the majority's decision was contrary to both law and equity. The case concerned a dispute over whether or not certain lands were subject to taxation by the federal government under an 1868 treaty with Native Americans. Justice Field argued that it would be unjust for Congress to tax these lands without first compensating their owners for them, as they had been acquired through treaties between sovereign nations which should be respected and enforced according to their terms. He further noted that if Congress could unilaterally impose taxes on such land without providing compensation, then any future treaties made with Native American tribes would become meaningless since they could simply be overruled by subsequent acts of Congress at any time. In conclusion, Justice Field concluded that while he agreed with the majority's interpretation of existing laws regarding taxation of Indian-owned land, he felt strongly that this ruling violated principles of justice and fairness towards Native Americans who had already entered into valid agreements with the U.S., thus making it wrongfully decided in his view