Serial killer Levi Bellfield is to marry after prison officials accepted they could not stop the ceremony going ahead.
Bellfield, 55, is serving two whole life orders for killing Millie Dowler, Marsha McDonnell and Amelie Delagrange.
He also tried to murder Kate Sheedy.
The Sun newspaper reports Bellfield was awarded up to £30,000 in legal aid to challenge the decision not to let him wed.
His lawyers cited the European Convention on Human Rights and the 1983 Marriage Act.
Bellfield also claimed to have been the victim of discrimination after officers banned him from wearing an engagement ring, the paper reports.
A Ministry of Justice spokesman said:
“Under current laws there are no legal routes to block this marriage and we recognise the pain and anger this outcome will bring to his victims’ families.
“It is what has driven our plans to stop prisoners on whole life orders from marrying in prison through our new Victims and Prisoners Bill – ensuring this never happens again.”
The Government has been trying to block the release of dangerous prisoners and ban criminals serving whole life orders from marrying behind bars under plans to overhaul the parole system.
Plans, unveiled in March, included the prospect of prisoners serving whole life orders – where the offender spends the rest of their life behind bars apart from in exceptional circumstances – being barred from marrying or forming a civil partnership in jail.
Dominic Raab, then Justice Secretary, said:
“There is a history of vulnerable women who have become pen pals with serial killers or particularly nasty offenders who get into relationships and then there is an issue around marriage.
“We’re doing this as a safeguarding issue but also as a public confidence in the justice system issue.”
Bellfield received a whole life sentence for the murder of Marsha McDonnell, 19, in 2003, Amelie Delagrange, 22, and the attempted murder of Kate Sheedy, 18, in 2004.
He was already serving his sentence when he went on trial for killing Milly Dowler.
She was snatched walking home from school in Walton-on-Thames, Surrey, in March 2002.
More than 60 criminals are believed to be currently serving whole life orders.