The Columbia University-educated doctor charged with promising to provide medical care to Al Qaeda operatives will argue that professional ethics require him to offer medical aid to all patients, even terrorists.

This legal defense by the accused doctor, Rafiq Sabir, is outlined for the first time in court papers submitted recently in Manhattan. Lawyers for Dr. Sabir will challenge whether rendering medical services to terrorists counts as providing “material support” to a foreign terrorist organization, which is illegal under federal law. The case against Dr. Sabir presents questions about the line separating an ethical physician from a terrorist supporter who happens to hold an M.D.

Dr. Sabir, of Boca Raton, Fla., is one of four co-defendants charged with a loosely connected plot to aid Al Qaeda that prosecutors made public last year. In a Bronx apartment in late May 2005, Dr. Sabir swore fealty to Osama bin Laden and pledged to provide medical assistance to jihadists who were wounded while training, a criminal complaint charged.

But in a recent court filing, Mr. Sabir’s attorneys, Edward Wilford and Natali Todd, argue that the prosecution is unconstitutional because it impinges on a doctor’s ability to practice medicine.

“As a medical doctor, Dr. Sabir is committed to saving lives, regardless of the status of the individuals because to do otherwise, would be to violate his cannons of ethics,” his attorneys wrote. “A doctor, similar to an attorney, should not be limited to who he can treat, however unpopular such an individual may be.”

The prosecution of Dr. Sabir, 51, and his three co-defendants is still in its early stages, and the judge, Loretta Preska of U.S. District Court in Manhattan, has not yet ruled on any of the defense’s motions to have the charges dismissed.

One medical ethicist said that doctors are bound to treat all patients, including the “jihadist in the emergency room.” But the ethicist, Robert Veatch of the Kennedy Institute of Ethics at Georgetown University, said yesterday, in a telephone interview that both professional ethics and the law would require that a doctor report the encounter afterwards to the authorities if there was reason to believe the patient intended to launch an attack.

Mr. Veatch said there was nothing inherently unethical about pledging one’s medical services to a specific group of patients, as Dr. Sabir is accused to have done. Mr. Veatch noted that doctors may decide to dedicate their careers to provide care to the indigent or to women who seek abortions, for example.

“I don’t think there is anything illegal with pledging to focus your practice of medicine on a certain type of patient, although it would probably be illegal if that meant you refused to provide aid for someone who wasn’t in the chosen group,” Mr. Veatch said.

Mr. Veatch anticipated that the government’s case could center around the oath of fealty Dr. Sabir allegedly swore to Osama bin Laden.

“Just because you are a physician doesn’t mean you are exempt from American law,” Mr. Veatch said. Legal observers have said that such an oath of fealty may be illegal under the material support statute as the law is currently written.

Dr. Sabir, a graduate of City College and Columbia University Medical School, is a licensed physician in New York. A devout Muslim, Dr. Sabir also practiced medicine at a military base in Saudi Arabia, he told an undercover FBI agent.

The criminal complaint filed last year does not indicate whether Dr. Sabir treated any known jihadists. The oath of allegiance to Mr. bin Laden that Dr. Sabir allegedly made in May 2005 occurred in the presence of an undercover federal agent posing as an Al Qaeda recruiter.

The material support law that Dr. Sabir is charged under does contain an exemption for providing medicine. Dr. Sabir’s lawyers argue in their legal brief that medicine consists not only of drugs and pills but also consists of a doctor’s services.

Lawyers familiar with Justice Department prosecutions say prosecutors seek to prove, with as much specificity as possible, exactly what type of aid the defendant sought to provide for a terrorist group.

Some courts, most notably the 9th Circuit U.S. Court of Appeals in San Francisco, have expressed skepticism with some aspects of the material support statute, which has emerged at the center of the Justice Department’s strategy in prosecuting terrorism charges.

Dr. Sabir’s attorneys argue that the law, originally passed in 1996 following the Oklahoma City bombing, is unconstitutionally vague.