62 HARVARD LAW REVIEW Between the two clear extremes there are many cases as to which there must be reasonable difference of opinion as to whether or not Congress is dealing with a genuine interstate matter. Such a case is the Lottery Act, the Pure Food and Drugs Act, the White Slave Act and the Child Labor Act. Statutes forbidding inter- state transportation of goods made by African slaves, or by con- victs, or by women at night, or of the product of sweat shops, or made by non-union labor, or by women and children employed at less than a minimum wage, may also be put in the arguable class. How shall it be determined that t^e problem is truly an inter- state one and the exercise of federal power is bona fide? Clearly not by the effect on the states, because that is as great in the one case as in the other. The question is essentially one of fact. Li determining the question definite rules have been long es- tablished. As an aid the court consults the legislative environment in which the act was passed, the Senate and House committee reports, and the history of the times. The prime consideration is the language used in the enactment. The dehberate legislative decision that interstate commerce power is being exercised is entitled to great weight. The legislature is a coordinate branch of the government. It has no prima facie case to overcome. It need not demonstrate its power under one particular theory rather than another. An enactment passed in due form cannot be upset on proof that a majority of the Repre- sentatives acted under erroneous views of legislative policy. If upon the face of the act any legitimate legislative purpose may be discovered, or rather, unless he who attacks can clearly show no possible proper purpose, the act must be sustained. To use the familiar language of the reports: "Every presumption favors constitutionaHty . ' ' Further, the question as to the existence of a genuine interstate problem is not to be complicated by the fact that solving it would also cure a local evil, and that in the minds of the public or of the members of Congress the local evil loomed large and induced action on the interstate matter. Such was the situation in the Lottery, Pure Food, White Slave, Liquor and Anti-Trust cases. It was the same in the prohibition of use of the mails to defraud. When the charge was made that a local police result was the ob- ject of the Prize-Fight Film statute, the court answered that it had
