The US of course. Look at the list of sites the plugin works for: none of them cares if you ignore their paywall. The likelihood that you would subscribe is negligible. It’s American readers they are after. And for them the jurisprudence is clear. No deliberate subversion of access controls allowed.
If that's the case Mozilla has no business banning the addon for everyone...
Mozilla is subject to US law. Mozilla has no obligation to enable certain addons only for visitors from certain countries.