In all democracies, a person is legally allowed to vote in one, and only one, voting jurisdiction. BWL

Not quite true. Here in the UK, you can be registerd to vote in more than one location.*

You can vote in elections in either location. You can vote in different locations on the same day, so long as it is at different levels, ie Vote in the nationals in place A, and the Local council elections in B. Of course, such an open system is easy to abuse, so it will be probabaly be changed, to something more complicated which does nothing to address the problem of elctoral fraud...



* This only generally happens to people with a reasonable claim to live in more than one loctaion, such as students who live with their parents outside of term time, or otherwise divide their time between two locations.