JMO but those specific kinds of rules belong within the franchise itself,not the NFL. If a franchise decides to sign a player with a sketchy background or a penchant for motorcycles (or basketball) then that's their decision to make and it's up to them to spell out whatever's necessary in the contract.
Not all players are irresponsible,not all players are stupid,and to mandate certain specific behaviors as NFL rulings really takes away from personal responsibility which should be inherent to a professional sport.
If the NFL dictated those things we wouldn't know who Michael Vick was,and the Bengals wouldn't exist.
I'd rather see the NFL stick with on-the-field issues like concussions,certain ref calls,etc than get into dictating players personal lives. The franchise should retain some freedoms and choices,the consequences of which they will have to live or die with.
More and more I see the importance of the Patriots' making character a priority,or at least as much as they can.Talent isn't everything,but that's a team assessment to make, not the NFL's. JMO.