The justices took a year to rule on a case that began in 1997, when George Zeliotis, an elderly Montreal man, tried to pay for hip replacement surgery rather than wait nearly a year for treatment at a public hospital.
Zeliotis told the high court that he suffered pain and became addicted to painkillers during the yearlong wait for surgery, and he should have been allowed to pay for faster service with private insurance.
"It is indeed a historical ruling that could substantially change the very foundations of Medicare as we know it," said Dr. Albert J. Schumacher, president of the Canadian Medical Association.
Although the ruling was made on the Quebec law, it likely will affect other Canadian provinces that forbid residents from buying private health care insurance for treatment under the country's Medicare system.
Opponents of changes to Medicare claimed it could force Canada into a two-tiered health care system in which those who have deeper pockets get faster, better service from doctors who opt out of the public health-care program.