I have had a very similar with Air France who I flew with once, through a "hacker" booking of a flight provided by Delta but through Air France's site to save hundreds of dollars over Delta's.
They actually subscribed me to four newsletters: "Flying Blue", "Hello from KLM US", "Air France USA", AND "iFly KLM Magazine United States". From those I've received ~75 messages over the past year.
Their unsubscribe links do not actually work. They prompt you to log in, but I can't log in to my account because I don't recall ever making one (and I'm diligent about storing passwords in a manager). Attempting to reset my password leads to a screen that says I'm locked out of my account for 3 unsuccessful attempts, and the only possible option is to call them. It's so broken. </rant>
IANAL, so I don't know if logging into an account would count or not. Personally, I see it as a hindrance to unsubscribing and by my reading of the CAN SPAM Act, it is illegal, but.. not a lawyer.
EDIT:
From https://www.ftc.gov/tips-advice/business-center/guidance/can... (which isn't the Act itself, but an FTC compliance guide):
Honor opt-out requests promptly. Any opt-out mechanism you offer must be able to process opt-out requests for at least 30 days after you send your message. You must honor a recipient’s opt-out request within 10 business days. You can’t charge a fee, require the recipient to give you any personally identifying information beyond an email address, or make the recipient take any step other than sending a reply email or visiting a single page on an Internet website as a condition for honoring an opt-out request. Once people have told you they don’t want to receive more messages from you, you can’t sell or transfer their email addresses, even in the form of a mailing list. The only exception is that you may transfer the addresses to a company you’ve hired to help you comply with the CAN-SPAM Act.
The absolute antibehavior of what you descrcribe I've recently experienced with Air Asia.
A few month ago they started to spam me with a newsletter I never requested. Last time I flew them was in the beginning of 2015 and I never subscribed for their crap.
The unsubscribe link on the mail does not work and after a significant amount of digging I found a way to unsubscribe by sending mail to [email protected].
Only that mail to this address is never delivered.
In essence there seems to be no way to unsubscribe from their list.
I mention that because it's infuriating that "reputable" companies think they can spam away with gusto without even the possibility to unsubscribe from their shit.
Here's a hint for you Air Asia: You are not reputable! You are on the same level as pushers of fake knock-off Viagra, purveyors of fake shlock Rolexes, and Nigerian scammers! And you will never, ever get an additional cent from me.
Scum!