The National Hockey League has been run questionably for some time now, trying to dictate which causes players can openly support while getting severe backlash and having to overturn some of those decisions, but, it doesn't stop them from telling players what they can and can't put on their equipment.
This decision by the NHL seems odd to say the least, especially given the recent reversal of the decision on Pride Tape and the fact that they've been a huge supporter of Hockey Fights Cancer in the past.
One has to wonder if the out cry of support to overturn this decision will be the same as the one we saw with Pride Tape. As it stands right now though, the NHL has made the decision not to allow a cancer ribbon on Thompson's helmet.