Sue. C’mon, you know you want to. Sue the league, Dan Snyder. What are you waiting for?

I can’t believe Snyder hasn’t already gone to court to ask for an injunction to hold up the start of NFL free agency. It’s the Washington Redskins’ last shot at getting back some of the salary cap space they lost last year when the league — quite ridiculously — decided that the Redskins and Cowboys violated a “gentleman’s agreement” in the writing of contracts in 2010, when there was no salary cap.

The Redskins certainly took advantage of that loophole, but a “gentleman’s agreement” seems like a fancy way of saying “collusion” to me. And it seemed that way to the NFLPA, although a federal judge has disagreed with the union, twice rejecting a collusion complaint. The bottom line: The league penalized the Redskins $36 million in cap space, split over two seasons. This season’s hit is $18 million.

A lawsuit filed by the Redskins — the Cowboys, who were not penalized as severely, won’t participate — would be an asteroid hurtling toward NFL free agency, which is scheduled to begin March 12. It’s probably not going to hit, but it’s the threat of impact the Redskins want. If it actually hit, then the league’s business calendar would be thrown into complete disarray. That might even ruffle Mel Kiper’s hair. Otherwise, so what? Snyder would be less popular among the league’s owners than he already is. Big deal. So he misses a few cocktail parties. If he was best buds with that bunch, you think we would be at this point now?

Some people tell Post reporters that the Redskins have compelling arguments to convince a judge that they would suffer irreparable harm if they are not granted an injunction. Others say they don’t believe the Redskins have a legal leg to stand on considering their arguments already have been rejected by an arbiter. Apparently the landmark case to-may-to v. to-mah-to will be cited as precedent.

Meantime, the Redskins are telling players and agents they can’t negotiate deals until the cap issue is resolved. That leaves them with two choices: swallow a bitter pill or sue the league. They’ve had months to think about this; what’s the holdup? Either do it or don’t.

I say do it.

If a man can file a $67 million lawsuit against a dry cleaner over a pair of lost pants — apparently, he left $66,999,900 in the pockets — then why can’t the Skins sue for $18 million in cap space? That’s four or five players, depending on how the money is spent. They’re already $4 million over the cap; in any case, they’ll have to cut players and/or rework contracts anyway. What have they got to lose?

Money, sure. It costs money to file a suit, even a suit over the loss of pants. (Would that still be a suit, or would it be a sports coat?) But this is a case of the rich suing the richer. And there’s no salary cap on the money an owner can spend suing the league — at least not yet. Don’t put it past Roger Goodell to come up with one, though.

Of course, a lawsuit would merely be a last-ditch attempt to get the league to reduce the amount of the punishment. There are risks. A suit also could crown Snyder as the league’s new Al Davis. Well, every organization needs someone to point out that the emperor is wearing no clothes. Snyder seems eminently suited to the role. Less palatable would be a backlash among agents, whose livelihoods depend on those contracts that the suit would delay.

A suit also could spur the league to be even more punitive toward the Redskins, although it’s hard to imagine a penalty stiffer than $36 million in players over two seasons. Some of Goodell’s recent attempts at discipline have backfired: His suspension of four Saints was overturned by former commissioner Paul Tagliabue. The league also faces thousands of lawsuits from former players of head injuries, probably including some inflicted under the Saints’ bounty system. Goodell’s got a lot on his plate.

So what does Snyder have to lose? Legal fees and goodwill in the league. What does he have to gain? Millions to spend on free agents and goodwill among Redskins fans. He needs the latter far more than he needs the former. So file already.