Whatever our incoherent laws say, I maintain that suicide is probably the most fundamental of human rights

Her attempts to guarantee the rights of people facing life's end were a different matter. The late MSP gave everything to her opponents, their deep beliefs, their fears, their moral and legal objections. Where morality in public life and law were concerned, Margo was scrupulous. Infuriating, but scrupulous. Always she had her trump-card question: "How is this fair?"

She had a specific purpose. How is it fair to force those who want a say in their dying to make the lonely journey to Dignitas at Forch, near Zurich in Switzerland, and end a life far from the sights, sounds and memories of home? How is any of it fair for those who can't afford the journey? And where's the fairness in laws that lay claim to the most fundamental choice an individual can make? Such laws do not just demand the obedience of a person. They demand - if this is the language of choice - your soul.

My view was always less forgiving than Margo's, but I've never had to frame or steer legislation. Whatever our incoherent laws say, I maintain that suicide is probably the most fundamental of human rights. Those who need or want that end should not have to burden those around them with the fear of prosecution. A world that has (just about) got the hang of birth control should find an equivalent in the personal, elected control of death.

Once again, the Scottish Parliament won't have it. Last week, Patrick Harvie's attempt to keep a promise to Margo failed by 82 votes to 36, with nine members failing to register an opinion. The Scottish Government opposed any alteration to existing law. Harvie aside, all the party leaders voted against his proposal. Meanwhile, those opposed to reform made a couple of excellent objections to the Assisted Suicide Bill. Rational defences of things as they stand were a little harder to find.

Still, I knew exactly what Nanette Milne of the Scottish Conservatives meant. A former anaesthesiologist with experience in oncology, she told the parliament: "Personally, as a former health professional, the idea of actively and deliberately hastening death by assisting someone to die is deeply disturbing for me. And I share the view of many professional colleagues that to legislate for this would risk undermining patient trust in doctors and medical advice."

There was merit, too, in the judgement of Alison Britton, convener of the Law Society of Scotland's health and medical law committee. She said the bill lacked clarity. In this sort of argument - though there is no other equivalent argument - a "robust and transparent process" is the minimum we require. That's obviously true. Terms such as "assistance" and "life-shortening" and "the functions of the licensed facilitator" cannot be vague.

Then again, give the dying, the distressed and the fearful, those who want choices while they can still make choices, and anyone else who would rather not live, a break. What's the first thing an adult knows about assisted dying in Scotland? That it goes on all the time. There is not an honest medical professional in the land who would deny it. The afflicted are aided towards their ends every day of the week, in every hospital in Scotland.

But no-one can say so. No doctor is allowed to suggest that the last truth could be managed better in the home, among familiar things and familiar faces. No patient can make the demand and expect to be heard. And no-one in the Crown Office has yet summoned the courage to issue the guidance guaranteeing that friends and family who hope to make the end of life a choice will not be prosecuted. That, as Margo would have said, isn't fair.

We each of us hope for a handful of things: no pain, no fear, clarity of mind, and acceptance. We are the only species on the planet to harbour such ambitions. I defer to no-one in my admiration for those who provide palliative care. It has progressed in my lifetime, like a philosophical argument, far beyond what was once imaginable. The astonishing people who provide pain control are meanwhile almost at the point of saying that no-one should ever suffer in the last days. This is remarkable. And still I want my rights.

Any good doctor can give you, in extremis, any amount of drugs, even while knowing that the narcotics involved will "hasten death". Nanette Milne is wrong, righteously, about that. In 2013, the former East Renfrewshire GP Iain Kerr admitted having given drugs ("medicines") to three people who felt "their lives had become intolerable". He was not prosecuted. A bad joke is hidden in the fact: there is no criminal offence of "assisting suicide" in Scotland.

You could be done for murder; you could wind up facing all manner of civil liabilities: the Crown Office, like the rest of us, isn't sure. Unlike some of the rest of us, the Crown Office doesn't appear to want to know. It returns us to Margo and her nagging principles. In this, of all things, ambiguity truly isn't fair. But ambiguity, once again, is all we're getting.

For me, for now, the arguments are theoretical. Should they become practical, the Crown Office can have my tinker's curse. Last week, Jeffrey Spector took his family and his inoperable tumour to Switzerland and made his choice, such as it was. In an interview, Spector said: "I know I am going too early, but I had consistent thoughts without peer pressure. It had to be a settled decision by a sound mind ... It is me who is doing this."

That ought to settle matters, even if the parliament of Scotland says otherwise: "It is me." The choice of suicide might challenge every tale of God and society, but it affirms the right, the final human right, of the individual: this body, that life, the brief interval amid the dark, surcease when the moment can no longer be delayed. Jeffrey Spector and his family had their happy faces on during their last meal in Switzerland. It's not much of a guess to suppose they would have been happier at home.

Of course no-one should be cajoled or coerced. Of course there should never be a sense of obligation laid upon the old or the sick. Of course - but why should it have to be said? - the miracle workers in hospices should always be there for those who make that choice of comfort. It is, in the end, just a small human argument over choices and fairness.

Scotland's parliament has preferred a legal muddle instead. And here's the problem: you cannot in honesty pass laws on behalf of lives when you deny the right to decide death.