SAN FRANCISCO – Each time the U.S. Supreme Court has ruled on medical marijuana, the justices have come down against allowing the sick and dying to use the drug to ease their symptoms and possibly prolong life.

However, the door has never been fully closed, and now a federal appeals court is set to hear arguments in the latest round of legal wrangling over the issue.

The case to be argued today before the 9th U.S. Circuit Court of Appeals in San Francisco narrows the matter to the so-called right-to-life theory: that marijuana should be allowed if it is the only viable option to keep a patient alive or free of excruciating pain.

It would apply only to the sickest patients and their suppliers, regardless of whether they live in one of the 11 mostly Western states that allow medical marijuana.

“A victory would affect people who are very seriously ill, facing death or great physical suffering,” said Randy Barnett, a Boston University law school professor working on the case.

The case was brought by Angel Raich, a 40-year-old mother of two from Oakland who suffers from scoliosis, a brain tumor, chronic nausea and other ailments. She uses marijuana every couple of hours to ease her pain and bolster her appetite.

“She’d probably be dead without marijuana,” said her doctor, Frank Lucido, who has recommended marijuana for some 3,000 patients. “Nothing else works.”

The Bush administration says the lawsuit is without merit.

“There is no fundamental right to distribute, cultivate or possess marijuana,” Assistant U.S. Attorney Mark Quinlivan, the government’s lead medical marijuana attorney, wrote to the appeals court.

Voters in 1996 made California the first state to authorize patients to use marijuana with a doctor’s recommendation. Ten other states have since followed suit but the federal government insists there is no medical value to the drug.

In 2001, the Supreme Court ruled that Raich’s supplier, the Oakland Cannabis Buyer’s Cooperative, could not lawfully dispense marijuana despite the California voters’ action.

Two years later, in a small victory for medical marijuana backers, the high court let stand a 9th Circuit decision saying doctors have a First Amendment right to discuss or recommend the drug to patients without the threat of federal sanctions.

But last June, the Supreme Court ruled the federal government could prosecute medical marijuana users and their suppliers.

In some states, federal agents have been sporadically arresting users and raiding so-called pot clubs that dole out the drug to patients. Raich herself was arrested this month for disorderly conduct while demonstrating outside the federal courthouse in Oakland over a recent raid on a medical marijuana dispensary.

However, a footnote by Justice Clarence Thomas in his 2001 ruling left the legal questions surrounding medical marijuana unsettled and helped open the door to Monday’s hearing.