The woman stands close to a mirror fingering her throat. Then, sweeping back a mane of red hair, she injects heroin into her jugular vein. A nurse keeps an eye on her from behind.

The scene unfolds in North America's first and only legal injection site, promoted by its founders as a safe, humane facility for drug abusers, now facing a court challenge from a government that sees it as a facilitator of drug abuse.

Defenders of the taxpayer-funded site, in a seedy, drug-infested district of Vancouver, British Columbia, say it is a providing a form of health care, and that health care is a provincial matter under Canada's constitution. The federal government counters that its writ trumps provincial rights because heroin is a federally banned substance.

The case opens before the Supreme Court of Canada in Ottawa on Thursday, and has drawn international attention. Insite, as the Vancouver center is called, is the only facility of its kind in Canada. More could open if the top court agrees Insite is legal.

As of 2009, there were 65 injection facilities in 27 cities in Canada, Australia, and western Europe, according to the Canadian Medical Association Journal. The World Health Organization has called them a "priority intervention" in slowing the spread of AIDS via infected needles.