Joseph McKenna, Shevlin-Carpenter Company v. Minnesota…
“ It is true that the police power of a state is the least limitable of its powers, but even it may not transcend the prohibition of the Constitution of the United States. If, as contended, intent is an essential element of crime, or, more restrictively, if intent is essential to the legality of penalties, it must be so, no matter under what power of the state they are prescribed. Plaintiffs in error, while considering there may be exceptions to the principle contended for in the exercise of the police power, urge that the legislation in controversy is not of that character. ”
