The constitutional court was asked to examine the case of Fabiano Antoniani, aka DJ Fabo, a music producer, left tetraplegic and blind by a traffic accident five years ago.
Italy's top court on Wednesday ruled that it should not always be punishable to help someone "under intolerable physical and psychological suffering" to commit suicide.
Anyone who "facilitates the suicidal intention... of a patient kept alive by life-support treatments and suffering from an irreversible pathology" should not be punished under certain conditions, the constitutional court ruled.
The patient's condition must be "causing physical and psychological suffering that he or she considers intolerable," it said.
The court was asked to examine the case of Fabiano Antoniani, aka DJ Fabo, a music producer, left tetraplegic and blind by a traffic accident five years ago.
Marco Cappato, a member of Italy's Radical Party, drove Antoniani to Switzerland in February 2017 where he was helped to die, aged 40.
Cappato then turned himself in to Italian authorities after his "act of civil disobedience" to highlight what he saw as an unjust law.
Cappato hailed the ruling in a tweet: "Those who are in Fabo's condition have the right to be helped. From today we are all more free, even those who disagree. It is a victory of civil disobedience, while the (political) parties turned their heads away".
Left-wing MP Nicola Fratoianni tweeted: "After the ruling, there are no more alibis: parliament should be capable of making a law of freedom for those who ask for self-determination and dignity for their lives."
A Milan court is trying Capatto on the charge of "instigating or assisting suicide", but asked the Italian Constitutional Court to clarify the current law.
The court last October gave parliament a year to fill a legal void on the question, but MPs have not done so.
A new government was sworn in last week after a month of political chaos, and debating assisted suicide is not one of its priorities.
"The current legal framework concerning the end of life deprives specific situations... of adequate protection," the court wrote last year.
Pope speaks out
Last week, Pope Francis spoke out against assisted suicide and euthanasia ahead of the ruling.
"We can and we must reject the temptation, which is also favoured by legislative changes, to use medicine to satisfy a sick person's possible wish to die," the pope told a delegation from the Italian Doctors Order.
The Church remains highly influential in the Roman Catholic country.
Euthanasia versus assisted suicide
The court case focused on assisted suicide, without mentioning euthanasia. The main difference lies in who performs the fatal act.
Euthanasia is an act aimed at intentionally causing the death of a patient with the will of the latter by a third party, usually doctor. Active euthanasia is when a lethal injection is practised. Passive euthanasia is when a life-saving drug is suspended, such as artificial hydration.
Euthanasia can be voluntary when it is requested by the patient, or it can also express the wishes of a third party, like a child.
Assisted suicide is the procedure chosen by Dj Fabo in 2017. In such cases, the patient asks the doctor to prescribe him some drugs that he himself will decide to ingest. Therefore the doctor does not act directly but assists the patient by collaborating with him.
End-of-life in Europe: state of the legislation
Only three countries in Europe allow both euthanasia and assisted suicide: Belgium, the Netherlands and Luxembourg.
Switzerland, Germany, Finland, and Austria allow physician-assisted death under specific scenarios.
Countries such as Spain, Sweden, England, Italy, Hungary, and Norway allow passive euthanasia under strict circumstances.