Use of another’s trademark is permissible if it qualifies as fair use. The fair use doctrine, consistent with the First Amendment, allows a person to use another’s trademark either in its non-trademark, descriptive sense to describe the user’s own products (classic, or descriptive, fair use) or in its trademark sense to refer to the trademark owner or its product (nominative fair use). The Lanham Act expressly protects fair use from liability for trademark infringement, dilution and cyberpiracy.

The Lanham Act specifies that good faith, descriptive fair use is an affirmative defense to an infringement claim. Before the affirmative defense is ever reached, however, the plaintiff must first show, as part of its prima facie case, evidence of likelihood of confusion from the defendant’s allegedly descriptive use of the trademark.

Comparative Advertising. In the United States, it is not an infringement of a trademark to use it in connection with accurate and non-deceptive comparative advertising. Truthful comparative advertising is considered to be beneficial to competition, provided that the use of the competitor' s mark is accurate and does not in any way imply an affiliation or endorsement by the trademark owner. Other countries have varying attitudes toward comparative advertising, so caution should be exercised with respect to advertisements directed to audiences outside the United States.