I wonder whether the regulatory / civil vs criminal distinction plays a role here.

It is plausible to assume that, at any given time, a random person from the juridisction A is in breach of compliance of jurisdiction B – knowingly or unknowingly to them. Jurisdiction B granting itself extra-territorial regulatory / civil (not criminal) enforcement powers puts the nationals of the entire jurisdiction A into non-compliance and subject to fines or arrests at the cross-border point. It is, of course, perfectly legally possible, yet surreal.

Curiously, what the UK is attempting in this instance closely mirrors the approach adopted by the CCP with the National Security Law in Hong Kong, wherein they asserted their own authority to indict any individual, of any nationality, residing in any jurisdiction, for alleged breaches of the Hong Kong NSL.

Whilst it is abundantly clear that the primary focus is Hong Kong pro-democracy activists holding multiple citizenships, they have also stated – with calculated lack of emphasis – that non-Hong Kong persons may likewise be targeted.