I think the penalty the 28 owners have imposed on the Cowboys and Redskins for structuring contracts in the uncapped year is probably illegal under anti-trust laws. I say this as an experienced attorney, though I am not an anti-trust lawyer.
Look at the 9th Circuit decision in the case filed by Al Davis when the NFL tried to prevent him from moving to Los Angeles. Here's a webpage devoted to the decision.
Davis charged that the League rule requiring owner approval of a franchise move violated the Sherman Antitrust Act. Here's what the jury found in that case.
"The jury found that Rule 4.3 (the rule requiring a vote of the owners to approve a move) violates § 1 of the Sherman Act, 15 U.S.C. § 1. Section 1 literally prohibits every agreement, conspiracy, or other concerted activity in restraint of trade. Since Congress could not have intended that courts invalidate “every” such agreement, most restraints are analyzed under the so-called “rule of reason.” The rule of reason requires the fact-finder to decide whether under all the circumstances of the case the agreement imposes an unreasonable restraint on competition."
Note that the issue here was owner v. owner restraint on trade, so the recent discussions about the NFL Players Association not being hurt by the league penalty is irrelevant. Clearly, 28 NFL owners have in this case decided to punish 2 teams severely (Washington and Dallas), and 2 teams less severely (Oakland and New Orleans) for structuring player contracts in a certain way in the uncapped year. This is equally clearly a restraint on competition, for a lot of reasons. It doesn't matter whether this is per se unreasonable; the question is whether a jury would find it unreasonable.
At this point, the real question is whether Dan Snyder and/or Jerry Jones have the stomach to sue the NFL, because the NFL will get away with this BS punishment if Jerry and Dan let them. I hope one or both of them bring a lawsuit, but I don't have that much hope of it happening. (Someone made the point that Jerry wants more Super Bowls in Dallas, for which he needs legitimate owner approval. That's probably worth more to him than rescinding the $10 million penalty.)
Where's Al Davis when you need him? The man was a crazy dude, but he knew how to stick it to the NFL.
What really gets me riled is when columnists like Sally Jenkins of the Washington Post blame this on Snyder (and Jones), without so much as a peep as to how outrageous the conduct of the 28 colluding owners was. I think Snyder's a royal jerk too, but in this case, it's the other owners whose conduct should be exposed for the illegal collusion that it is, not Snyder.