In the 1992 case of Walter L. Nixon v. United States, former federal judge Walter L. Nixon challenged his impeachment and removal from office by Congress after being convicted of perjury in a criminal trial. He argued that the Senate had violated the Constitution's Impeachment Trial Clause because it appointed a committee to hear evidence instead of conducting proceedings before the full Senate body. The Supreme Court ruled unanimously against Nixon, upholding his removal from office as constitutional. The court held that questions regarding impeachment and removal are non-justiciable political issues; they cannot be reviewed by courts because they involve discretionary powers granted to another branch of government (in this case, Congress). Therefore, how the Senate chooses to conduct an impeachment trial is entirely its own decision. This ruling affirmed that judicial review does not extend into matters explicitly delegated by constitution to other branches - reinforcing separation of powers principle within U.S government structure.

In the dissenting opinion for Walter L. Nixon v. United States, Justice White argued that the Court should not have dismissed Nixon's claim as a nonjusticiable political question. He contended that while impeachment is indeed a political process, it does not mean that no aspect of it can be reviewed by the judiciary branch. The Constitution provides specific requirements for impeachment and removal from office - namely conviction of "high Crimes and Misdemeanors." If these terms are to have any meaning at all, they must be defined in some way by either Congress or the courts; otherwise, there would be no limit on what could constitute an impeachable offense which goes against constitutional principles. Furthermore, he pointed out that if this case were truly nonjusticiable due to its nature as an 'intra-branch' dispute between members of Congress and a federal judge (as opposed to an inter-branch dispute), then many other cases involving disputes within one branch would also become unreviewable - something he found untenable.