Isn't it? Shouldn't it be a violation of basic contract law? Especially if you've already flown the outbound segment, or like the one person paid by debit, how can AC decide it's "not satisfied" with the payment after it has the funds in the bank? They simply decided to not perform the contract. If AC isn't satisfied with the payment, why refund the amount?

There has to be consequences for non performance of the contract, and the guy in NL unsurprisingly won his court case against AC. No amount of weasel words in fine print can overcome that.

Stranding passengers and forcing them to pay a much higher price over the refunded amount to get home doesn't make the passenger whole, performing the contract does.