I’m concentrating here on UK general elections; the rules for local elections and for EU elections are rather different.
Who can and can’t vote in the UK at general elections?
While we think we have universal adult suffrage, this is not quite correct. You must be on the electoral register, be over the age of 18, and be a British citizen, a citizen of the Republic of Ireland or a citizen of some commonwealth countries.
You cannot vote if you are an attending member of the House of Lords, an EU citizen who is resident in the UK, if you are a convict in prison, or if you have been convicted of electoral fraud within the past five years.
Who can and can’t be a candidate in UK general elections?
This is specifically about N Ireland, though the requirements are similar elsewhere in the UK.
You must be at least 18, a British citizen, a citizen of the Republic of Ireland or of a qualifying commonwealth country, or a citizen of Malta or Cyprus.
You cannot be a candidate if you are a civil servant, as the civil service is expected to be non-political; a member of a police force or the armed forces; a judge, a member of an external parliament (except the Dáil/Oireachtas), a Lord Temporal or a Lord Spiritual sitting in the House of Lords. (In the past, if you were in the armed forces wanted out, you could apply for a release from your service if you were an election candidate. This became so popular that the rules, inevitably, were made quite restrictive.)
Certain bankrupts are disqualified, as are many convicted prisoners, or if you have been convicted of electoral fraud within the previous five years.
Being a MEP is ‘incompatible’ with being an MP. You cannot stand in more than one constituency at the same general election.
Note: the eligibility to vote and to be a candidate, and what can disqualify you from voting or being a candidate is much more complicated than this brief summary outline indicates.
You can see that (many) convicted prisoners can neither vote nor be a candidate—the rules around this are, again, much more complex than my simplistic overview. But these restrictions do raise some fundamental questions; and there has been conflict between the UK government who have wished to restrict prisoners’ rights and the European Court of Human Rights (ECHR)—another reason why the present Tory government wants to replace the Human Rights Act with a ‘British’ one.
Not that long ago, the punishment for most crimes, particularly property crime, was hanging—even for quite trivial theft. Public opinion gradually swung against this; transportation was introduced. The ideas of the Enlightenment in general, and Jeremy Bentham in particular informed modern prison theory. There were three main components to this; punishment through imprisonment for wrong-doing; deterrence to minimise reoffending, and put others off; and rehabilitation, an attempt to return convicts to a useful function in the outside world.
Rather oddly, the practical implementation of this model was based on the prior experience of the Magdalen Institutes in the 18th century; these had been established by both concerned protestant and catholic worthies, starting in London and Dublin, and operating for several decades. They are not to be confused with the Laundries, a different punitive concept, despite the similarity in name. (The Wikipedia entry is not correct.) The original Institutes were set up to house, sequester and rehabilitate ‘fallen women’. The Institutes chose those who they felt were capable of rehabilitation, those who were ‘penitent’—the origin of the US name for a prison, the ‘penitentiary’. The women who were taken in were clothed in fairly coarse, plain clothes; fed, taught a trade such as needlecraft and given hefty doses of Christian religiosity and morality. They were also paraded as a spectacle for (morally superior) onlookers on Sundays. At the end of three years or so, the women were released on licence, with a small amount of money, and expected to find their way in the world—the forerunner, if you like, of parole. The system wasn’t perfect, but it did work for many.
Restricting prisoners’ ability to vote, to take part in the political process, can be seen as a swing from rehabilitation to punishment.