The murderers of Lee Rigby could be sent to prison for the rest of their lives after a crucial court ruling.
The Court of Appeal has said 'whole-life' sentences, where convicted criminals are jailed for an unlimited term, are legal.
In doing so, it defied a European Court of Human Rights ruling in July, which said whole-life sentences were unlawful because there was no prospect of review.
The punishments have been handed to some of the most heinous criminals of recent years, including one-eyed cop killer Dale Cregan and child-murderers Mark Bridger and Levi Bellfield.
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Sentencing in a number of high-profile criminal cases was put on hold - including the terms to be handed out to soldier Rigby's murderers - pending the judgment.
And it has provoked a row over the power of Strasbourg courts to determine what happens in the UK.
Speaking on the Today programme on Tuesday morning, Tory MP Dominic Raab said: "It's perfectly reasonable for a democratic society to say that life should mean life for the very serious and dangerous criminals we are talking about."
Such matters had nothing to do with torture or human rights, he said, but was European judges "trying to push their progressive agenda by the back door".
But leading human rights lawyer Baroness Helena Kennedy QC said the debate was not about jailing people for life.
What was needed was a "just in case provision", she said, "just in case something has to be looked at at that point.
"It's about fairness and justice."
It was about "setting a standard" for places like Russia, where they do "throw away the key", she said.
In their ruling, the Court of Appeal ruling found that the UK system of whole-life sentences did allow for a review and that judges should be confident to continue using them for the most serious crimes.
A panel of five judges, headed by the Lord Chief Justice Lord Thomas, announced their decision on controversial "life-means-life" orders at the Court of Appeal in London.
The judges increased the 40-year minimum prison term being served by killer Ian McLoughlin, who murdered a man while on day release, to a whole-life tariff.
And they dismissed an appeal by Lee Newell, who murdered a child killer while in prison, against the whole-life order imposed in his case.
The Government has said that whole-life tariffs are "wholly justified in the most heinous cases".
Reacting to today's ruling Attorney General Dominic Grieve said on Twitter: "I am pleased CoA (Court of Appeal) has confirmed those who commit the most heinous crimes can be sent to prison for the rest of their lives."
Grieve added: "As someone who has killed three times, Ian McLoughlin committed just such a crime, and following today's judgment he has received the sentence that crime required.
"I asked the Court of Appeal to look again at McLoughlin's original sentence because I did not think that the European Court of Human Rights had said anything which prevented our courts from handing down whole life terms in the most serious cases.
"The Court of Appeal has agreed with me and today's judgment gives the clarity our judges need when they are considering sentencing cases like this in the future."