> Is there some law stating that if you host a website
You're looking at this backwards.
The TOS is not a contract that automatically applies to everyone; I don't have to agree to it if I link to your site.
Generally, if you want to prevent people from using your website in a certain way (that's not blatant abuse/hacking/etc), you're going to have to resort to technical solutions, because your only legal recourse is copyright law, which may or may not apply.
> Is there some law stating that if you host a website
You're looking at this backwards.
The TOS is not a contract that automatically applies to everyone; I don't have to agree to it if I link to your site.
Generally, if you want to prevent people from using your website in a certain way (that's not blatant abuse/hacking/etc), you're going to have to resort to technical solutions, because your only legal recourse is copyright law, which may or may not apply.