15 U.S.C. § 1111: Notice of registration; display with mark; recovery of profits and damages in infringement suit

Notwithstanding the provisions of section 1072 of this title, a registrant of a mark registered in the Patent and Trademark Office, may give notice that his mark is registered by displaying with the mark the words “Registered in U.S. Patent and Trademark Office” or “Reg. U.S. Pat. & Tm. Off.” or the letter R enclosed within a circle, thus ®; and in any suit for infringement under this chapter by such a registrant failing to give such notice of registration, no profits and no damages shall be recovered under the provisions of this chapter unless the defendant had actual notice of the registration.