In the United States v. Lovett case of 1945, the Supreme Court ruled that Congress had overstepped its constitutional authority by passing a bill effectively punishing three government employees without trial. Robert Lovett, along with Goodwin Watson and William Dodd Jr., were accused of being "subversive" due to their alleged communist affiliations. In response, Congress passed a law in 1943 denying them further salary payments from federal funds - an act considered as legislative punishment or 'bill of attainder', which is prohibited under Article I Section 9 of the U.S Constitution. The court held this action unconstitutional in a unanimous decision (8-0), asserting that only courts could impose such punishments after proper trials have been conducted.

In the dissenting opinion for United States v. Lovett, Justice Frankfurter argued that Congress had not overstepped its bounds by refusing to pay salaries of government employees it deemed subversive. He asserted that the Constitution grants Congress control over appropriations and therefore has the power to decide how federal funds are spent. Furthermore, he contended that this was not a case of legislative punishment or bill of attainder as claimed by majority but rather an issue related to national security during wartime where Congress acted within its rights in protecting against potential threats from within government ranks. The dissent also emphasized on respecting separation of powers and cautioned against judicial interference in Congressional matters unless there is clear violation of constitutional provisions.