"NOTE: THIS IS 100% LEGAL! SEE SECTION 1302 OF THE US CODES, PART 18!!"
OK, I thought: I'll bite. Fully expecting to find no such code or "part," I instead immediately Googled up this interesting law.
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Whoever knowingly deposits in the mail, or sends or delivers by mail:
Any letter, package, postal card, or circular concerning any lottery, gift enterprise, or similar scheme offering prizes dependent in whole or in part upon lot or chance;
Any lottery ticket or part thereof, or paper, certificate, or instrument purporting to be or to represent a ticket, chance, share, or interest in or dependent upon the event of a lottery, gift enterprise, or similar scheme offering prizes dependent in whole or in part upon lot or chance;
Any check, draft, bill, money, postal note, or money order, for the purchase of any ticket or part thereof, or of any share or chance in any such lottery, gift enterprise, or scheme;
Any newspaper, circular, pamphlet, or publication of any kind containing any advertisement of any lottery, gift enterprise, or scheme of any kind offering prizes dependent in whole or in part upon lot or chance, or containing any list of the prizes drawn or awarded by means of any such lottery, gift enterprise, or scheme, whether said list contains any part or all of such prizes;
Any article described in section 1953 of this title - Shall be fined under this title or imprisoned not more than two years, or both; and for any subsequent offense shall be imprisoned not more than five years.
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This would seem to rule out the Publisher's Clearinghouse Sweepstakes (not that we get that anymore).