One of democracy’s ideals is egalitarianism: Each person gets one vote, and all votes are equally consequential, so that all people have equal power over the world. For that reason we consider it improper for one person to vote twice in the same election. But then shouldn’t we also consider it improper for dual citizens to cast votes in two different places?
It’s true that dual citizens vote in different elections, but they’re still exercising twice as much power over the world as other voters. And it’s true that power is already unequally distributed among the world’s voters, but this is no reason to shrink from the ideal.
The fact that a dual citizen has the legal right to cast two ballots doesn’t mean that this accords with democratic principles. Suppose that Texas passed a law saying that any native-born Texan can vote in Texas, regardless of where he currently lives. Then a Texan living in Pennsylvania could cast ballots in both states, whereas a native Pennsylvanian could vote only once. This might be legal, but we would object morally to the unfairness of such a law.
Given the unequal influence of the world’s nations, one idealistic way to equalize power among all voters would be to give everyone a right to vote in every election, everywhere. This would give each of us an equal amount of power over the world. “That vision remains pretty visionary, we concede,” write Robert E. Goodin and Ana Tanasoca. “Still, visions matter.”
(Robert E. Goodin and Ana Tanasoca, “Double Voting,” Australasian Journal of Philosophy, vol. 92, no. 4, 743-758.)