The landmark ruling was made in regards to euthanasia activist Marco Cappato, who was accused of assisting suicide after helping 40-year-old Italian disc jockey Fabiano Antoniani, or DJ Fabo, to die at a Swiss euthanasia clinic in 2017.
Antoniani was left blind and quadriplegic by a serious car crash in 2014.
He also required assistance breathing and eating.
Antoniani had said that the crash left him in a world of “physical and mental pain”.
He fought for his right to die in Italy, before choosing to end his life at the clinic in Switzerland.
Antoniani’s death became the subject of fierce debate in a country where euthanasia is opposed by the Catholic Church.
The Church sees euthanasia as the morally unacceptable killing of a person and a violation of the law of God.
On Thursday, it said it had “distanced” itself from the decision by the country's constitutional court, which it viewed with “discontent”.
Cappato has praised the court ruling, saying that “as of today, all of us in Italy are freer”.
The constitutional court also called on parliament to pass legislation on the issue of assisted dying.
Cirinnà, a Senator for the centre-left Democratic Party (PD), said parliament must pass legislation on the subject “soon” and do it “well”.
Far-right League leader Matteo Salvini said he would never allow “suicide by law” in Italy.
Giorgia Meloni, head of the rightwing Brothers of Italy (FdI) party, said the ruling was a defeat for parliament and for the nation.
