MARGO MacDonald is not an easy woman to refuse. She has a habit of getting her way.

When she fell foul of the Scottish National party leadership, she stood as an independent MSP and won. Her warnings about the incompetence of those building the Scottish parliament at Holyrood proved to be incisive. When she turns her attention to a subject, whether improved PE in schools or extra funding for Edinburgh, Scotland pays attention.

It is difficult to imagine MacDonald being denied something as personal as the timing of her departure, either from the Holyrood chamber or this earth. But the law of the land can and does say no to Margo. That is why this week she made a moving appeal to be given the right to die.

MacDonald has suffered from Parkinson's disease for the past 12 years. As a result, her delivery of those famously feisty one-liners is more deliberate than of old, and there is some evidence of the slight tremor that characterises the condition. But illness has done nothing to diminish the energy with which she serves her Lothian constituents.

MacDonald, however, warned that this might change. She could find herself among an unfortunate minority of those suffering the most severe form of Parkinson's. In that case, she argued, she might prefer to go at a time of her own choosing, rather than be a burden on her family.

“I would like to have the right to determine by how much my capacity to fulfil my social function, my familial functions, my personal functions is going to be truncated,” she told her colleagues during a debate on terminal illness.

The very personal nature of her intervention dominated media coverage of the Holyrood debate to which she was contributing. But hers was not the only worthwhile contribution, as she would be the first to acknowledge. We always notice when MSPs say stupid things, fall over their words, grandstand or fiddle their expenses. So when they do something right, it's worth drawing attention to it.

The intelligent debate was instigated by Jeremy Purvis, the Liberal Democrat member whose assisted- suicide bill was thrown out several years ago. He was at pains to point

out that he was not proposing euthanasia. His proposal would not affect children, the infirm, the elderly or the depressed. It would apply only to competent people who had been told by two doctors that their illness was

terminal - people, perhaps, such as MacDonald eventually. Purvis pointed out that it is lawful to withdraw lifesaving treatment from individuals in a vegetative state. But people in possession of their faculties are refused the right to die — a strange contradiction.

Set out in this manner, the case for changing the law appears straightforward. But it is anything but simple. How does one distinguish the competent patients from elderly, sick people who might feel pressurised to give up, or believe that dying is more dignified than the shoddy care they receive?

The Conservative MSP Mary Scanlon, who was once a nurse, pointed out that it can be difficult to interpret the wishes of a terminally ill person if they are delirious, confused or demoralised. Ian McKee, the SNP MSP who was a GP before entering parliament last year, could think of only one or two patients in his long career who “genuinely wanted to end their lives at a time chosen by them.”

Both McKee and Labour's Richard Simpson, another doctor turned politician, drew attention to the advances in palliative care for the dying in recent decades. Simpson is an expert in this field, having helped to manage one of Scotland's first hospices in the 1970s, yet he admits he still “wrestles” with the issues. The rise of the hospice movement and the growth in size and influence of cancer care organisations such as MacMillan and Marie Curie mean that more attention is paid to the dying, their right to dignity, the choice of where they spend their last days and, of course, freedom from pain. It is not so long ago that patients were abandoned in impersonal hospital wards or simply dumped at home with no support except for bewildered relatives - if they were lucky. It was, said Simpson, “a disgrace”.

Despite the progress that has been made, it is generally agreed that we have some way to go, particularly in allowing patients to get the best possible care at home. Fortunately, cancer patients now receive a far better service, thanks to the specialised nature of their condition, and powerful lobbying. But those dying of other diseases are less fortunate.

This ought to be the government's priority. A report published last May by the Scottish Partnership for Palliative Care made 16 separate recommendations, most of which focused on how to make sure everybody in the country requiring palliative care received the same “gold standard”. Nicola Sturgeon, the Scottish health secretary, will shortly publish an action plan based on these recommendations, but, along with her counterparts in England and Wales, she faces new challenges with every step towards progress. How, for example, are the dying to be treated in a system where out-of-hours care is worse than it was 20 years ago? The rest of us gripe about NHS 24, but imagine how much worse they are to deal with if you are in your last days of life?

The rows around out-of-hours care are financial ones; assisted-suicide laws should be considered within this context. Health systems, whether funded by taxation or insurance, are subject to the same budgetary pressures as everything else. Think of postcode prescribing, the GP's contract and hospital closures.

Palliative care is expensive because it demands specialised nurses and doctors. Can we really be sure that the introduction of euthanasia will not slow down the steady improvements in this area of medicine? This is why the British Medical Association is so opposed to any change, and why most MSPs, including Sturgeon, support this position. Doctors are the people who negotiate daily with NHS managers on behalf of their patients — they know the pressures.

During the debate, Dr Richard Simpson said there would always be a small number of cases in which death was “difficult, troubled and disturbing for the individual and the relatives.” Let us hope that Margo Macdonald is never among this number. If she were, I would hope we could find a way to accommodate her wishes without endangering others.

I suspect, however, that such a law cannot be drafted.