Idaho Admin. Code r. 04.02.01.064
It is an unfair and deceptive act or practice for a seller to offer goods or services by representations comparing the prices of the seller's goods or services to the prices of comparable, but not identical, goods or services of a competitor's, unless the seller can substantiate that the goods or services compared are substantially similar in grade and quality and the represented prices of the competitor's goods or services are in fact the actual prices charged by the competitor in the same trade area, at the same point in time or on the date(s) clearly and conspicuously disclosed in the advertisement. If a price is stated without clear and conspicuous disclosure of a date on which it was in effect, it shall be presumed to be the current price.
Idaho Admin. Code r. 04.02.01.064