First off, fans have no standing to file suit. So you can drop that thought.
The teams and players could be the applicants for injunctive relief.
The fact that there was "unofficial agreement" or "edict" to really have an unofficial salary cap in 2010--an agreement that is not part of the CBA--is an agreement itself that is a price restraint not evidenced by the CBA which is the exclusive location for such agreements per the NFL's anti-trust exemption.
For those that aren't certain, here is a very simplistic explanation of the law: 32 companies cannot get together and decide they'll have a cap (or floor) as to how much they are willing to pay. That conduct violates the Sherman Antitrust Act.
So for example, say the 5 biggest computer manufacturers said "we will not pay more than $1 for a processor." That would be the same as the salary cap, because paying for labor is the same as paying for component parts. Well, processor makers would be forced to sell for that amount because it is an agreement between the guys who control the market.
That is "price-fixing" or "price restraint" and it is prohibited anti-competitive behavior.
Congress granted the NFL a waiver of anti-trust allegations when the merger occurred. That allowed the NFL to engage in such decisions but the only mechanism by which they are permitted to do it with respect to labor is through the CBA. It is the exclusive mechanism. If they are making agreements not contained in the CBA, they have a problem.
This also has an over-lapping issue with the NLRA as it relates to the wages of a union separate from the CBA, which is the exclusive bargaining provision for working with a union.
This is really a legally dicey move by the NFL.
I've seen some suggestion that this was an agreed result. If that is the case, then it may be a non-issue. But I have a hard time believing Jerry agreed to this. And if it a punitive measure against a dissenting voter, there are other issues regarding collusion.
I'll be interested to reading the formal wording of this because it smacks of being problematic.
Oh, and if there are equally bad "violaters" but certain firms are singled out for punishment, it makes it more likely this is anti-competitive behavior (as the standards are adjudged on a rule of reason that looks for neutral application).