The Belfast teenager is likely to become the first killer in the Island to have a minimum sentence set by the Royal Court.
Under the current law the court can only advise on a minimum sentence but the final decision rests with the UK Home Secretary.
But the States yesterday passed a law to allow the Royal Court to set the minimum length of sentence that a murderer will serve.
And the Attorney General, William Bailhache, told the House that, under transitional powers that cover a person found guilty of murder before the law comes into force, he would be applying to the Royal Court to order a mandatory minimum sentence for Greenan, who was found guilty of the murder of nursery nurse Tracy Burns last week.
He is due to be sentenced in July.
Previously all criminals sentenced to life imprisonment in Jersey were sent to a prison in the UK, where the Secretary of State had the power to extend a sentence or release a prisoner early.
But in 2002 the House of Lords ruled that this power, although lawful, was not compatible with human rights legislation.
