In Palmore v. United States (1972), the U.S Supreme Court upheld a conviction by a non-Article III court, specifically the District of Columbia's local courts which were created by Congress and not under Article III of the Constitution. The defendant, Johnnie Mae Palmore, was charged with robbery and assault in D.C.'s Superior Court but argued that his case should have been tried in an Article III federal court instead. He contended that this violated his Fifth Amendment rights to due process and equal protection under law. However, the Supreme Court ruled 8-1 against him stating that while Article III protects certain judicial functions at a federal level from political or public pressures, it does not guarantee all litigants access to these courts for trial of all matters. It further stated that Congress has significant leeway to create legislative courts like D.C.’s Superior Court for special purposes such as governing territories or military bases.

In the dissenting opinion for Palmore v. United States, Justice Douglas argued that the use of a non-Article III court in this case violated the Constitution's separation of powers and infringed on individual rights. He contended that Congress cannot create courts with judges who lack life tenure and protection against salary reduction to try serious criminal cases because it undermines judicial independence, which is crucial for safeguarding citizens' constitutional rights. The majority's reliance on historical practice was deemed insufficient justification by Justice Douglas as he believed such practices were not always constitutionally sound or consistent with principles of liberty and justice. Furthermore, he expressed concern about potential abuses if Congress could freely assign its judicial power to tribunals lacking Article III protections.