The beginning of Justice Kagan's dissent in AMEX v. Italian Colors Restaurant says it all:
Here is the nutshell version of the case, unfortunately obscured in the Court's decision. The owner of a small restaurant (Italian Colors) thinks that American Express (Amex) has used its monopoly power to force merchants to accept a form contract violating the antitrust laws. The restauranteur wants to challenge the alleged unlawful provision (imposing a tying arrangement) but the same contract's arbitration provision prevents him from doing so. That term imposes a variety of procedural bars that would make pursuit of the antitrust claim a fool's errand. So if the arbitration provision is enforceable, Amex has insulated itself from antitrust liability -- even if it has in fact violated the law. The monopolist gets to use its monopoly power to insist on a contract effectively depriving its victims of all legal recourse.
And here is the nutshell version of today's opinion, admirably flaunted rather than camouflaged: Too darn bad.