The ACLU has published this report. From the report:

This report offers the first in-depth analysis of the criminal disfranchisement policies of the world’s democracies, with a focus on Europe. (We do also examine, though perhaps not in the same depth, other developed democracies’ policies and precedents, namely those of Israel, Canada, Australia, New Zealand and South Africa.) Simply describing these laws accurately has proven a surprisingly difficult task; a few previous authors have attempted to do so, focusing their attention mostly on documents such as constitutions and election-law statutes.6 We have drawn on their important work here, but have found that constitutions and statutes alone often fail to deliver a full understanding of a given country’s disfranchisement policies and practices. In addition to such formal legal sources, this report benefits from exhaustive research into legislative materials, judicial proceedings, advocacy reports, and numerous other sources, including information from original surveys and interviews with governmental and non-governmental officials of several countries. No previous publication has synthesized so much country-by country disfranchisement data, decisions of high courts, and international legal instruments.
Following this Introduction, Section II of the report describes the policies of European nations, and Section III offers detailed summaries of the decisions rendered by various countries’ constitutional courts in the last decade. Section IV examines mechanisms used in various democracies to implement prisoner voting, and Section V considers treaties and other legal instruments, both binding and advisory, which bear on the voting rights of people with criminal convictions.
These are among the central findings of this study:
– Almost half of European countries allow all incarcerated people to vote while others disqualify only a small number of prisoners from the polls. As we explain below, almost all of the countries that disqualify all inmates are in Eastern Europe.
– In most countries where disfranchisement does exist, the policy is both more narrowly targeted and more visible in its application than in the United States.
– A number of treaties and other types of international instruments support either the abolition of criminal disfranchisement law, or considerably narrower restrictions than those employed by most American states.
– All foreign constitutional courts that have evaluated disfranchisement law have found the automatic, blanket disqualification of prisoners to violate basic democratic principles. In countries where courts have called for enfranchisement of inmates, the legislative and executive branches have complied without significant resistance.
– Where prisoners are allowed to vote, they do so either in the correctional facilities themselves – with no threat to security – or by some version of absentee ballot, in their town of previous residence, in all cases with government entities facilitating the voting. In no country do prisoners vote in a manner that allows them to shape the politics of the prison locality.
Readers will have different responses to this evidence. Some will deduce from the widespread and unproblematic fact of prisoner voting elsewhere that the United States should promptly overhaul its policies. Others may scoff, perhaps having already concluded that the ideas and policies of other countries are and should remain irrelevant to the American political context.
We believe no less an authority than the American Declaration of Independence counsels against the latter conclusion. As Jefferson famously wrote, “a decent respect to the opinions of mankind requires” that we be able to explain the reasons for our policies to others. While it is not our view that the international setting alone justifies a change in American law, we do argue that the evidence compiled here should induce greater skepticism about the wisdom of disfranchisement law in the United States.
In our view, this evidence, coupled with the serious and extensive problems these laws pose for both the officials administering them and those affected by them, counsels in favor of rethinking the broad bans and replacing them with rational, tailored bans, or none at all. Given the relative ease (and low cost) of administering absentee ballot voting in prisons, states may want to seriously consider the examples of Maine, Vermont and Puerto Rico. Or, following the example of some European democracies, consider barring only those it makes sense to bar – for example, those convicted of election fraud. Another possibility would be to enfranchise all except the incarcerated, with no documentary requirement complicating reinstatement on the rolls after release from prison. Although such a policy now survives only in the most regressive European nations, it would constitute a significant movement forward for most American states, given how far out of step the United States is on this issue. Moreover, inmate-only disfranchisement – if you are able to appear physically at the polls and meet age and residency requirements, you are eligible to vote – would solve the multitude of problems now bedeviling the administration of disfranchisement policies in the U.S.