The league and players association also agreed last fall that players who enter the league must wear helmets that meet safety standards. But some players…wear noncertified helmets. They were grandfathered into the agreement so they could continue to wear their lighter helmets. NHL director of hockey operations Brian Burke calls them "cereal boxes with chin straps."

Gretzky is the highest-profile player who continues to wear an unapproved "cereal box," but he is not alone.

Gretzky, Detroit's Igor Larionov and New York Ranger defenseman Marty McSorley wear helmets similar to Goulet's, made by the Swedish company JOFA. Castaldi said Gretzky's helmet "is like a cereal box."