In truth, this really isn't about PEDs. Again, the NFL has a policy for that. This is another maneuver in the now-ubiquitous power struggle between the league and its players. The NFL is emboldened by its legal victory over Brady and is using the same broad authority -- as written in Article 46 of the collective bargaining agreement -- to compel participation in an otherwise out-of-policy investigation.
If you celebrated Brady's discipline, surely you realized that your team could be next. You did realize that, right?
At the moment, it's difficult to imagine the limits of the league's power. Even in a union environment, with a legal CBA in place, we might finally have reached the moment when players are subject to discipline whenever they don't do what the NFL asks of them.