In the 1988 case Mistretta v. United States, John Mistretta challenged the constitutionality of the Sentencing Reform Act of 1984, which established the United States Sentencing Commission. The commission was tasked with creating guidelines for federal criminal sentencing to reduce disparities in sentences handed down by different judges. Mistretta argued that this violated separation of powers principles because it gave judicial power to a body within another branch of government (the executive). However, the Supreme Court upheld both the act and creation of commission as constitutional in a 8-1 decision. The court ruled that while Congress had indeed delegated significant authority to an independent agency within Judicial Branch, it did not violate separation-of-powers principle since adequate guiding standards were provided by Congress and no single branch amassed more power than others through this arrangement.

In the dissenting opinion for Mistretta v. United States, Justice Scalia argued that the Sentencing Reform Act of 1984 violated the separation of powers doctrine because it delegated excessive legislative power to a commission within the judicial branch. He contended that Congress had abdicated its responsibility to set criminal penalties and instead improperly transferred this authority to an unelected body, thereby undermining democratic accountability. Furthermore, he expressed concern about judges serving on such a commission as it blurred their roles between being impartial adjudicators and policy makers which could potentially compromise their independence and neutrality in sentencing decisions. In his view, this arrangement was inconsistent with constitutional principles designed to prevent concentration of power in any one branch of government.