The Harper government has asked the Supreme Court of Canada to ignore mounds of evidence trumpeting the success of North America’s first supervised injection site for drug users, warning that the court should avoid becoming a “super legislature” by ruling on the wisdom of federal policy decisions.

The caution is contained in Justice Department legal arguments filed in the Supreme Court for a hearing Thursday that will determine the fate of Insite, the safe-injection site located in Vancouver’s notorious Downtown Eastside. Insite is an eight-year-old facility where addicts can inject their drugs using sterile needles under a nurse’s supervision.

Ottawa contends that its power over criminal law trumps British Columbia’s jurisdiction over health care in deciding whether the unique clinic should survive.

“Public safety demands that access to drugs be carefully controlled,” federal lawyer Robert Frater says in a legal brief.

The B.C. government, in its written submission, counters the case boils down to “which level of government has the final say on the local delivery of vital health care services within a provincially authorized health care facility.”

The hearing is the latest and final legal showdown in an intense battle that has persisted since the Harper Conservatives refused three years ago to renew a Health Canada exemption that permitted to facility to operate in contravention of criminal drug laws.

The federal government, in its written arguments, note that the clinic operators have filed “a prodigious amount of material” that aims to show safe-injection sites prevent overdose deaths, contain the spread of HIV/AIDS, reduce public disorder in the neighbourhoods where they are located, have wide support, and result in more addicts entering detox and treatment programs.

“The issue of whether supervised injection sites are good public policy is not a matter for the courts,” says the federal legal brief.

“Absent the exercise of restraint, the courts risk becoming a super-legislature…”

The clinic, which opened in 2003 under the Liberal government of Jean Chretien, initially operated under a three-year exemption from Health Canada, so that staff and clients were shielded from criminal charges.

When the Harper government declined in 2008 to extend the exemption, then health minister Tony Clement said at the time that “every dollar” of the $3 million spent annually on the clinic was a dollar not spent on drug treatment.

The federal government is bringing the appeal to the Supreme Court following two defeats in the British Columbia courts.

The B.C. Court of Appeal ruled in January 2010 that the clinic falls under provincial jurisdiction over health care so the federal government does not have the power to shut it down.

The British Columbia Supreme Court went even farther, concluding in a 2008 ruling that shutting down a health-care facility that saves lives and curtails the spread of infectious disease violates the Charter of Rights guarantees of life, liberty and security of the person.

The B.C. Court of Appeal said it wasn’t necessary to rule on Insite’s constitutional right to stay in business because it had already decided the clinic was a provincial responsibility.

The Portland Hotel Society, a community organization that helps house homeless drug addicts, and the Vancouver Area Network of Drug Users initially launched the court challenge.

“At issue in the appeal is nothing less than the ability of the province to respond to an epidemic, and the rights of injection drug users to try to survive it,” PHS lawyer Joseph Arvay says in written legal arguments to the Supreme Court. He says that the federal government’s broad claim that criminal law should prevail “has the potential to exert a stranglehold on the provincial health care power, and imperil the rights – and lives – of some of Vancouver’s most disenfranchised residents.”

The B.C. government, which is also a party in the case, has kept the clinic open while the case winds its way through the courts.

The appeal has drawn 11 intervenors, including the province of Quebec, which is a strong proponent of decentralized health care, and several public health groups and civil libertarians.

In the event that the court rules against the federal government, the Justice Department wants the ruling suspended for one year to give Ottawa time to regroup.

After a prolonged dearth of division-of-powers cases in recent years, this is third federal-provincial jurisdictional dispute before the Supreme Court in the last five months. In December, the Supreme Court ruled, in a deeply divided decision that sided with Quebec, that much of Canada’s thriving fertility industry falls under provincial control over health care rather than federal control over criminal law. In another case last month, the court was asked to decide who has the power to regulate the Canadian stock markets — the federal government or the provinces. A decision is pending.