You say this, but it's been prosecuted in enough cases that are often posted to Hacker News, I don't even feel compelled to find a link to show that... deleting

You say this, but it's been prosecuted in enough cases that are often posted to Hacker News, I don't even feel compelled to find a link to show that... deleting your account and informing you by e-mail that you have been banned and your accesses of the web services provided by a brand are no longer welcome are valid standards of "denying access." They can block your IP address, but that's been held up as an example of "how not to implement a service block" enough times already, I think the important bit is above.