This Sunday, when the camera zooms in for a closeup of the National Football League action, look carefully at the helmets. Chances are you will see the ) word Riddell emblazoned on the nose guard. Riddell Inc. of Chicago has 60% of the N.F.L. helmet market and a peculiar contract: if players use another brand of helmet, they must cover the maker's name. Riddell won that provision in return for supplying N.F.L. teams with free helmets, pads and jerseys.
Illegal procedure, says the country's only other major helmet producer, Athletic Helmet Inc. of Litchfield, Ill. A.H.I. has filed suit in federal...