A terminally ill man should not have to endure a "distressing and undignified" death because of the ban on assisted dying, the Court of Appeal has heard.
Noel Conway, 68, of Shrewsbury, who has motor neurone disease, is challenging the current law on assisted suicide.
He wants the right to enlist medical professionals to end his life when he feels it has become unbearable.
Nathalie Lieven QC said it was for Mr Conway to decide a matter as "intimately personal" as how he dies.
Mr Conway, a retired lecturer, wants to be helped to die, which the current law prevents, when he has less than six months to live, still has the mental capacity to make the decision which has made in a "voluntary, clear, settled and informed" way.
Outlining Mr Conway's case to senior judges, Sir Terence Etherton, Sir Brian Leveson and Lady Justice King, his legal team said the current law interfered with his rights and the court must decide whether that interference was "justified and proportionate".
Ms Lieven said: "The question for this court is not a very generalised one of the morality or ethics of allowing doctors to assist patients to die.
"The question for this court is rather a focused one of whether for this very specific cohort, ie, terminally ill people with less than six months to live, the ban is justifiable because of an impact on the weak and vulnerable."
She said there was "serious objective evidence" which led Mr Conway to conclude there was a genuine risk death would not be "quick and painless" if he refused ventilation.
Ms Lieven said: "Mr Conway reiterates that, if suitable safeguards are in place, the wider interests of society cannot possibly be said to require him to undergo such a death in the name of securing against possible risks to weak and vulnerable individuals."
He is too ill to travel to London for the hearing, expected to last three days, so watched proceedings via video link at Telford Justice Centre.
Mr Conway, who says he feels "entombed" by his illness, said he felt "quietly optimistic" about the hearing's outcome.