The UK is considering making it illegal to reidentify anonymous data.

I agree that this should not apply to researchers, but if it is limited to commercial activity and public relations or campaign activity, it would be ethical.

Would it be enforceable? If the penalties are sufficiently strong, organizations aiming for profit or other success would hesitate to violate the law.

The law needs to address the scenario where the reidentification is done in some other country but the usage is targeted at people in the UK. Usually some organization that operates in the UK will be paying for the service. If that organization can be identified and punished, that might make the law enforceable enough.