Unlike other professional careers (eg: accounting, finance, consulting etc..), law is more geographically restrictive because legal systems remain very different, "cross qualifying" into working in other jurisdictions usually involves more professional exams and sometimes academic study too. The US is even more fractured with qualification being at a state rather than federal level.
That's not to say you can't work overseas as a lawyer but generally speaking, if a lawyer who's qualified in England & Wale or Scotland is working overseas they will probably be working for an overseas office of one of the large UK centered firms, or a US firm with a large London presence. It's pretty rare for a UK lawyer to actually qualify directly as a French or German lawyer for example.