Whole-life jail terms without the possibility of review amount to a breach of human rights, European judges have ruled.
The case was instituted against the UK but the implications are international.
In Malta, before the last general election, the NGO Mid-Dlam ghad-Dawl said that life term imprisonment should be replaced by indefinite terms, and those sentenced to such terms should be eligible for parole.
The case before the European Court was instituted by murderer Jeremy Bamber and two other killers, Douglas Vinter and Peter Moore.They won an appeal in the Grand Chamber of the European Court of Human Rights that their sentences amount to inhuman and degrading treatment.
The court found that for a life sentence to remain compatible with the European Convention on Human Rights there had to be both a possibility of release and a possibility of review. However, the panel of 17 judges added: "In finding a violation in this case, however, the court did not intend to give the applicants any prospect of imminent release."
The appeal was brought by Vinter, who stabbed his wife in February 2008, and means the cases of Bamber, who killed his parents, sister and her two young children in August 1985, and Moore, who killed four gay men for his sexual gratification in 1995, will also be considered.
In their ruling, the judges said it was up to the national authorities to decide when such a review should take place. However, existing legal comparisons gave support to guaranteeing a review no later than 25 years after the imposition of a life sentence.
Under current UK law, whole-life tariff prisoners will almost certainly never be released from prison as their offences are deemed to be so serious. They can be freed only by the Justice Secretary, who can give discretion on compassionate grounds when the prisoner is terminally ill or seriously incapacitated.
The court also found that the current law concerning the prospect of release of life prisoners in England and Wales was unclear. The judges added whether Bamber, Vinter and Moore should be released would depend on whether there were still legitimate grounds for their continued detention and whether they should continue to be detained on grounds of dangerousness. Up until 2003, there was a right to review for all whole-life orders in the UK but this was removed in a change of legislation.
Vinter's lawyer Simon Creighton, of Bhatt Murphy Solicitors, said the ruling could not be used as a "get out of jail free" excuse for life-term prisoners.
Bamber, 51, has been behind bars for more than 25 years for shooting his wealthy adopted parents June and Neville, his sister Sheila Caffell and her six-year-old twin sons Daniel and Nicholas at their farmhouse in Tolleshunt D'Arcy, Essex. He was given a whole-life tariff after being convicted of the murders in October 1986.
Vinter was released from prison after serving nine years for the 1995 murder of work colleague Carl Edon, 22 - but just three years later he stabbed his wife Anne White four times and strangled her, and was given a whole-life order. Welsh serial killer Moore was convicted of four counts of murder in 1996 after killing four gay men across a period of four months.