The US National Football League (NFL) is insisting players should only wear uniforms that it agrees to.

The sport's governing body has imposed fines on players breaking strict dress codes when they customise their kits. In several recent cases, players who wanted to commemorate lost loved ones have faced opposition from the league.

The NFL is requiring that players support cancer awareness by wearing pink on the field during October.

But it is refusing to allow the campaign to continue past the end of the month.