The NFL is seeking more than $1 billion from its insurance carriers in connection with the settlement of a class action suit arising from the claim that the NFL concealed the long-term risks of head trauma from its players.

The NFL, however, doesn't want insurance carriers to find out what the league knew and when the league knew about the head trauma risks.

Insurance companies have begun the process of enforcing “long-standing subpoenas” for documents regarding head injuries from the NFL’s 32 teams. 

The move comes amid a two-year fight over the limits of permissible “discovery” in the lawsuit.