American Needle Inc. v. New Orleans Louisiana Saints et al., No. 04 C 7806, 2005 WL 1126537 (N.D. Ill., E. Div. May 5, 2005): 

Plaintiff held a non-exlusive license from the NFL to create apparel and headwear with NFL team logos.  The NFL didn’t renew and granted Reebok and exclusive license.  Plaintiff sued on antitrust grounds arguing that the NFL was attempting to monopolize the market in NFL-logo merchandise.

From Findlaw’s account of the District Court decision

The defendants had argued trademarks only indicate the source or sponsorship of goods or services and say nothing about which other products consumers might see as substitutes.

While that is usually true, the judge said, here the NFL team logos can be viewed as the actual product. While some people might buy a T-shirt or hat with a logo just because they need a T-shirt or hat, most people who buy logo-bearing merchandise are fans who would not see other kinds of apparel as a reasonable substitute, the judge said.

The NFL’s motion to dismiss was denied for 4 of the 5 counts and the case continues.