This is, in practice, true which has led to the other complaint common on tech forums (including HN) about paywalls. As the WSJ and NYT will tell you: if you request some URL, they can respond over the wire with what they want. Paywalls are the future. In some sense, I am grateful I was born in the era of free Internet. In my childhood, without a credit card I was able to access the Internet in its full form. But today's kids will have to use social media on apps because the websites will paywall their stuff against user agents that don't give them revenue.
They're welcome to send that IMO. And sites are welcome to try to detect and ban agents (formerly: "bots").
As long as it's not wrong/immoral/illegal for me to access your site with any method/browser/reader/agent, and do what I want with your response. Then I think it's okay to send a response like "screw you, humans only"
Paywalls suck, but the suck doesn't come from the NYT exercising their freedom to send whatever response they choose.
Yes, that's what I mean. Attempting to tell people not to do something is like setting a robots.txt entry. Only a robot that agrees will play along. Therefore, all things have to be enforced server-side if they want enforcement.
Paywalls are a natural consequence of this and I don't think they suck, but that's a subjective opinion. Maybe one day we will have a pay-on-demand structure, like flattr reborn.