Identification of a problem does not mean that the government should undertake to solve it, and the fact that a problem occurs in more than one state does not mean that it is a proper subject for federal policy.
Perhaps no area more clearly demonstrates the bad consequences of not following such rules than does drug prohibition. The long federal experiment in prohibition of marijuana, cocaine, heroin, and other drugs has given us crime and corruption combined with a manifest failure to stop the use of drugs or reduce their availability to children.