The Supreme Court yesterday declined to disturb a ruling that the federal government can't be sued to compel it to provide medical care to servicemen whose health may have been imperiled when they were exposed to cancer-causing radiation in nuclear bomb tests in Nevada in 1950s.

Rejecting a plea by a former soldier with spreading, inoperable cancer, the justice let stand a decision by the 3rd U.S. Circuit Court of Appeals that soverigh immunity - the doctrine that the government can be sued only with its consent - prevented him from seeking medical care for hundreds of thousands of military personnel who had been exposed.

The former soldier, Stanley Jaffee, Was drafted into the Army, served two years and was honorably discharged Jaffee is a pharmacist in River Edge, N.J., married and has three children.

Jaffee, now 47, was found in November 1977 to have breast cancer and underwent a radical mastectomy. He is receving chemotherapy.

In 1953, he was among a group of soldiers who were ordered to stand in open trenches a short distance from the site of the explosion of a nuclear device at Camp Desert Rock, Nev. They had no protective clothing or gear to shield them from radiation. After the expolosion, officers ordered them to leave the trenches and march toward the explosion site.

In a multifacted complaint Jaffee first of all sought a court order forcing the government to notify all of the men who were put at risk. That issue is pending before U.S. District Court Judge Herbert J. Stern in Newark.

Jaffee also seeks damages from the officers who, he alleges, "deliberately and knowingly" violated his constitutional rights by neither advising him of the hazards nor giving him a chance to refuse to particpate. Judge Stern has yet to decide whether those defendants are immune from liability.

Finally, Jaffee asked that the government be required to provide or subsidize medical care for all of the men who were exposed. On this issue, the 3rd Circuit blocked him on the ground of soverign immunity, agreeing with the government that the classfication was a disguised damages suit to which it had not considered.