In the US, all voting laws and procedures are determined by the various states, so there could be 50 different standards, but I think the usual rule is that convicted felons permanently lose the right to vote.

It doesn't matter to me very much whether felons vote or not. I doubt that it will make any difference in the outcome of any election.

The problem is, if you forbid felons to vote, how do you enforce that rule? Do you require every law-abiding voter to prove that he is NOT a felon before you allow him to vote? In other words, do you require him to show a state-issued picture ID card with a magnetic stripe on the back, so you can check his identity against a database of all non-felonious citizens?

If you require the card, you would be disenfranchising everyone who fails or refuses to obtain and carry the card. This would disproportionately affect the young, the poor, and the less educated. Would this not be a greater evil than allowing the occasional felon to vote?

That's the debate we've been having in the US lately. Felons are not supposed to vote, but the Republicans are claiming that too many of them vote anyway; and therefore we need tougher enforcement, which means ID cards. It's a favorite Tea-Party issue.