That may be fraud, since fraud is the making of a false statement of fact to induce someone to rely on that fact and enter into a transation, while knowing--or at least, the speaker reasonably should be aware--that the statement is false. Affirmatively representing that  these items were new while knowing that he had no basis for that assertion may make the dealer guilty of fraud. This is also likely a breach of contract case: the ad would essentially be integrated into the contract, since it described the item you were buying, and so you did not get what you paid for. Or alternately, the contract of sale could be rescinded due to mutual mistake: you and the dealer both thought these items were new, but they were not, meaning you were both mistaken as to what you were agreeing to and there was no "meeting of the minds." Therefore, there are three possible grounds for either rescinding the sale or seeking compensation.