In the U.K. Labour Party leadership election, 2015, people who want to vote need to register as members or supporters can vote. But what are the U.K. residency requirements to register as a supporter and vote? Can anyone or Earth vote, only U.K. citizens, or is the criterion somewhere in-between?
Anyone wishing to participate in the Labour leadership elections, needs to be registered to vote in the U.K. That means the requirements are identical to those for participating in elections.
For participating in ordinary national elections, one must have British citizenship. However, this does not apply to the Labour leadership elections.
(Source: personal communication from Labour)