Actually it is.

According to Equal Credit Opportunity Act specifically 15 U.S.C. § 1691(a)(3), it is illegal for a creditor to take any credit related action against a consumer who exercises a protected consumer right in good faith.

While I agree and concede not every consumer case (including Chase's closure) involves a protected consumer right, still creditors are cautious in closing accounts, or taking retaliatory actions, against those who threaten to sue, sue or sued creditors.

IIRC - a few months ago, a FTer's account has been shut down, as the FTer claimed the reason of the closure was the chargeback (I don't exactly remember Chase or Citi). In this case, because the FTer exercised a protected consumer right, as soon as the right was exercised in good faith, closing the account could be deemed as a retaliatory action. The issuer could in fact be liable for the actual damage (from the chargeback), a up to $10,000 punitive damage, as well as a court order commanding the re-opening the account.