Eugene Traynor started drinking to intoxication before he was 10 years old. James P. McKelvey was an alcoholic at 13. Both went into the Army, both got out with honorable discharges and for a time both kept on boozing. Now they are plaintiffs in a case before the U.S. Supreme Court that could profoundly affect an estimated 10 million alcoholics in the United States.

If the high court takes a broad view of the case, private and public employers could find themselves under new obligations. Companies writing health and hospitalization insurance would feel the impact. The key question, if the court wishes to face it, is as old as it is troublesome: Is alcoholism a disease? Or is it what the Veterans Administration terms ''willful misconduct''?

These were the facts: Traynor enlisted in the Army in 1968, but his drinking caused such medical and disciplinary problems that he was discharged in 1969. Over the next five years he was hospitalized five times for alcoholism. The Veterans Administration diagnosed his condition as ''primary'' alcoholism, a term used to denote alcoholism without an underlying psychiatric disorder.

In 1977 Traynor licked the demon. He invoked his educational benefits under the GI Bill of Rights and enrolled in college. Under the law, such benefits must be used within a 10-year period following discharge. Traynor's time ran out in August 1979. He applied for an extension, arguing that his illness, i.e., his alcoholism, had prevented him from taking full advantage of the program. The VA rejected his petition under a longstanding regulation. In the VA's view, Traynor's ''willful misconduct'' was all his own doing.

McKelvey followed the same path. He was discharged honorably in 1966, then hospitalized 33 times for alcoholism before he joined Alcoholics Anonymous and put booze behind him. He too used some of his educational benefits before time ran out, and he too was refused an extension.

Both veterans brought suit in federal courts, and both won at the trial level before losing in the circuit courts of appeal. They argued that Congress itself had defined alcoholism in a 1970 act as ''an illness requiring treatment and rehabilitation.'' In support of their position they cited an impressive array of medical opinion.

The National Council on Alcoholism has filed a friend-of-the-court brief in their behalf. In the council's view, alcoholism ''is neither misconduct nor a moral failing, but a complex and insidious medical condition that can and must be treated.'' The government's position is ''archaic, erroneous and stigmatizing.'' The alcoholic is a handicapped person under the Rehabilitation Act of 1973. Excessive drinking ''is not something over which he or she has conscious or voluntary control.'' The council notes that the World Health Organization defined alcoholism as a disease in 1951, the American Psychiatric Association in 1953 and the American Medical Association in 1956.

It is quite possible that the Supreme Court will sidestep the broad question altogether. The Veterans Administration operates under a peculiar system almost unmatched elsewhere in the bureaucracy: final decisions of the Board of Veterans Appeals are not subject to judicial review. The 2nd U.S. Circuit cited this fact in its divided opinion rejecting Traynor's claim.

This immunity, however, applies only to ''any law administered by the Veterans Administration providing benefits to veterans.'' Is the Rehabilitation Act such a law? It protects handicapped persons from discrimination in any program receiving federal benefits. The government contends that the VA does not administer the Rehabilitation Act; the VA administers only acts affecting veterans.

There the jurisdictional argument stands. The Supreme Court traditionally refuses to get to the merits of a case if there is any plausible way of avoiding the merits on technical grounds. The theory is that it is better to leave essentially statutory questions up to Congress, and there is much to be said for that theory. It would be a simple matter for Congress to rewrite the VA regulation on ''primary'' alcoholism if Congress agrees with the medical opinions.

I take no sides on this one. Over a long life in the newspaper business I have known a good many alcoholics. Were my friends sick? Were they handicapped as handicaps are usually understood? Or did they simply lack the self-discipline to control their drinking? Perhaps the high court will say.