indirectly through Wiki
According to league policy, no NFL owner may own, directly or indirectly, any interests in a gambling casino.
another in relation to Kraft selling land near Gillette to a casino
The National Football League prohibits teams from owning casinos, and a league policy warns of potential severe penalties for any league personnel, including owners, who associate "with gamblers or with gambling activities in a manner tending to bring discredit to the NFL."
edit - missed by that much