What the alternate entry method (for someone who doesn't do business with the advertiser) does is morph the lottery into a sweepstakes. State laws on sweepstakes are a real patchwork, so you need to be careful about where you offer such a promotion and how it operates. But if you don't have the alternate entry method, you're looking at a lottery, and federal laws prohibit the participation of a bank or savings association in lotteries (there are not similar federal prohibitions for credit unions, as I recall).
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John S. Burnett
BankersOnline.com
Fighting for Compliance since 1976
Bankers' Threads User #8