In a landmark ruling, the European Court of Human Rights decided life prison terms with no prospect of release were a violation of human rights.
The court's Tuesday ruling, 16 to 1, stated that life sentences without parole violated article 3 of the European Convention of Human Rights, which prohibits inhuman and degrading treatment.
The ruling, sought by convicted murderers Jeremy Bamber, Peter Moore and Douglas Vinter, does not mean there is "any prospect of imminent release" for the three men. It only holds that whole-life jail terms without a chance at freedom are inhumane.
"For a life sentence to remain compatible with article 3 there had to be both a possibility of release and a possibility of review," said the judgment, which applies to England and Wales. The two countries cannot appeal the verdict, and have six months to consider their response, according to the BBC.
In response to the news, David Cameron's spokesman said the British prime minister was a "strong supporter of whole-life tariffs (sentences)" and "profoundly disagrees with the court's ruling."
According to the court: "If such a prisoner is incarcerated without any prospect of release and without the possibility of having his life sentence reviewed, there is the risk that he can never atone for his offense: whatever the prisoner does in prison, however exceptional his progress towards rehabilitation, his punishment remains fixed and unreviewable."
However, the court added: "the finding of a violation in the applicants' cases should not be understood as giving them any prospect of imminent release. Whether or not they should be released would depend, for example, on whether there were still legitimate penological grounds for their continued detention and whether they should continue to be detained on grounds of dangerousness."
The ruling overturns a judgment from January 2012 in which seven European court judges ruled the life sentences of Vinter, Bamber, Moore and some 46 other prisoners, did not violate article 3.
As the law stands, a prisoner who receives a whole-life sentence is not eligible for parole and can only be released on compassionate grounds if, for example, he or she is terminally ill. The prisoner's sentence can be shortened upon winning an appeal.