In 1975, in a case involving food safety, the Supreme Court said that defining the outer bounds of criminal liability could be entrusted to "the good sense of prosecutors, the wise guidance of trial judges, and the ultimate judgment of juries." United States v. Park, 421 U.S. 658, 669 (1975) (quoting United States v. Dotterweich, 320 U.S. 277, 285 (1943)). Such willingness to trust a prosecutor's "good sense" is hardly the case now. In McDonnell v. United States, 579 U.S. 550, 576 (2016), to take one example, the Supreme Court declined to construe a key phrase affecting the definition of bribery expansively "on the assumption that the Government will 'use [a criminal statute] responsibly'" (citing United States v. Stevens, 559 U.S. 460, 480 (2010)).

This concern with how broadly worded statutes may be used, or misused, by prosecutors was central to the Supreme Court's decision last term in Ruan v. United States, 142 S. Ct. 2370, 2380 (2022). Ruan arose from a federal criminal prosecution of licensed physicians for over-prescribing opioids and other addictive drugs, in violation of §841 of the Controlled Substances Act. That law prohibits distribution of controlled substances "[e]xcept as authorized." 21 U.S.C. §841.

The Supreme Court considered whether "authorization" in that context should be based on a defendant's subjective knowledge and beliefs or an objective standard of reasonable medical care. The court held that authorization is a subjective matter and clarified that the government bore the burden of disproving a claim of authorization when properly raised by a defendant. Declining to rely on "the good sense of prosecutors," the court chose to construe the "[e]xcept as authorized" clause in a manner that imposed a heavier burden on the government before treating conduct as criminal in nature.