The Federal Trade Commission put the rule in place back in 1971 and amended it in 1989.
The FTC stated, “The Unavailability Rule, issued in 1971, prohibits retail food stores from advertising prices for food, grocery products, or other merchandise unless they have the advertised products in stock and readily availability at, or below, the advertised prices.”
The 1989 amendments granted stores some flexibility, with excetions where “the advertisement clearly and adequately discloses that supplies of the advertised product are limited or . . . available only at some outlets.”
FTC added, “Retail food stores do not violate the Rule if they (a) order advertised products early enough and in sufficient quantities to meet ‘reasonably anticipated demand,’ (b) issue rainchecks for the advertised products, (c) offer comparable products at comparable prices, or (d) offer other compensation at least equal to the advertised value.