The Revenue Act of 1951, levied a tax on persons engaged in the business of accepting wagers and required such persons to register with the Collector of Internal Revenue. The statute imposed a special tax of $50 per year and required each person to register all the contact information. An information was filed against D alleging that he was in the business of accepting wagers and that he willfully failed to register for and pay the occupational tax in question. D moved to dismiss because the statute was unconstitutional. The District Court dismissed and reasoned that while 'the subject matter of this legislation so far as revenue purposes is concerned is within the scope of Federal authorities,' the tax was unconstitutional in that the information called for by the registration provisions was 'peculiarly applicable to the applicant from the standpoint of law enforcement and vice control,' and therefore the whole of the legislation was an infringement by the Federal Government on the police power reserved to the states by the Tenth Amendment. The Supreme Court granted certiorari.