The campaigners from disability group The Distant Voices created a "giant graveyard" outside the Royal Courts of Justice to highlight the danger of the court ruling in favour of Noel Conway.
"The bottom line is it's just too dangerous," said Nikki Kenward, a Christian who organised the protest. "We've seen in every country that it's been made legal that the use of it spreads in the most terrible way."
Kenward, who has Guillain-Barré syndrome, also told Premier: "Should Mr Conway win his case it will change my life forever. As a disabled person I am only too aware that some people see me as having 'no quality of life.' A young friend, who has cerebral palsy, and I, were told by a youth worker, 'If I were you two I'd rather be dead.' Please don't tell me I will not be vulnerable if euthanasia is legalised."
Conway, a 68-year-old retired lecturer from Shrewsbury, wants to be helped to die - which the law currently prevents - when he has less than six months left to live, still has mental capacity to make the decision and has made a "voluntary, clear, settled and informed" decision.
He has proposed that he could only receive assistance to die if a High Court judge determined that he meets all three of those criteria.
Outlining his case to three senior judges on Tuesday, Mr Conway's lawyers said the law as it stands interferes with his rights and that the court must decide whether that interference is "justified and proportionate".
Mr Conway previously asked the High Court for a declaration that the Suicide Act 1961 is incompatible with Article 8 of the European Convention on Human Rights, which relates to respect for private and family life, and Article 14, which protects from discrimination.
His case was rejected in October last year, but a full appeal against that ruling will begin on Tuesday.
Mr Conway is too unwell to travel to London for the hearing but has been watching proceedings over a video link from Telford Crown Court.
In a statement ahead of the hearing, he said he is now dependent on a ventilator for up to 23 hours a day and only has movement in his right hand, head and neck.
Mr Conway said his current options are to "effectively suffocate" by choosing to remove his ventilator or to spend thousands of pounds travelling to Switzerland to end his life and have his family risk prosecution.
His appeal is opposed by the Secretary of State for Justice while Humanists UK are supporting Conway's argument.
The appeal is expected to last three days.
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