In in the United States, it's usually the Superior Court judge that decides if your competent to vote. In Washington state, it's on a case-by-case basis. You can have a guardian and vote, but not if the state is your ward.
Related:
Polish Presidential Election - Voting in EnglandMoved from Poland to England several years ago and wish to vote in the Polish Presidential election. Anyone know if there is a facility to do this in Yorkshire.
emito.net/wiadomosci/polityka/jak_glosowac_w_uk_na_prezydenta_rp__736346.html
leeds-manchester.pl/artykul/671/jak-w-uk-glosowac-na-prezydenta-rp.html