Trademark disparagement is a cause of action that allows a party to petition the Trademark Trial and Appeal Board (TTAB) of the USPTO to cancel a trademark registration, if the registration "may disparage or falsely suggest a connection with persons . . . institutions, beliefs, or national symbols, or bring them into contempt or disrepute."
After the USPTO refused to allow registration of the term "The Slants", on the basis that it is disparaging under 15 USC 1502(a), the applicant appealed the matter to the Federal Circuit. A Federal Circuit panel first affirmed, based on In re McGinley, 660 F.2d 481 (CCPA 1981), finding no violation of the First Amendment, as the applicant was nontheless free to use the mark without registration.
However, a later en banc panel of the Federal Circuit granted further review, and found that 1502(a) did violate the First Amendment, as the disparagement provision is neither conent or viewpoint neutral, and that the loss of a federal government right, even standing alone, has a chilling effect on speech.
The full case and opinion can be found at -- http://www.cafc.uscourts.gov/sites/default/files/s14-1203_Opinion_2-11-2016_1-correted.pdf