In the case of United States v. Balint et al., 1921, the Supreme Court ruled that a defendant could be convicted for violating federal narcotics laws even if they were unaware that their actions were illegal. The defendants, Mr. and Mrs. Balint, had been charged with selling drugs without an order form as required by law at the time but claimed they didn't know about this requirement. The court held that ignorance of such regulatory statutes does not exempt individuals from prosecution under them because these types of laws are enacted to maintain public welfare and safety rather than punish morally culpable behavior specifically.

In the dissenting opinion for United States v. Balint et al., Justice McReynolds argued that the defendants could not be held criminally liable under the Narcotic Act of 1914 because they were unaware that they were dealing with narcotics, specifically opium and cocaine. He contended that criminal liability should require knowledge or intent as a necessary element, which was absent in this case. The majority's interpretation of the law would result in punishing individuals who unknowingly commit an offense, which he believed to be fundamentally unjust and contrary to traditional principles of criminal law. This view emphasizes individual moral culpability over strict legal interpretations.