The Justice Department said yesterday that because of a legal technicality, only current federal workers, and not retirees, are entitled to share in a $289 million premium rebate proposed by Blue Cross-Blue Shield, the nation's largest health insurance company.

But a top official of the Office of Personnel Management said President Reagan had been briefed on the issue and was considering authorization of refunds to all the company's 1.5 million federal policyholders, about half of whom are retired.

"We are confident that a means can be developed" to get the refunds -- ranging from $18 to $374 -- to retirees, too, the company statement said. About 220,000 of the subscribers live in the Washington area.

The OPM, which runs the federal insurance program, asked Justice for a legal opinion on the refunds after the insurance company made the unprecedented offer in May to return millions of dollars to subscribers and to the federal government because of a 22 percent drop this year in health care claims.

Reagan was briefed on the issue Thursday and is expected to make a decision shortly, officials said. The OPM official, who asked not to be identified, said the president "is disposed to make the refunds to everybody . . . including retirees."

The Justice opinion said the federal insurance act authorizes premium cuts or refunds for "employes" but does not mention "annuitants." Federal officials said that is believed to be a technical oversight that could be remedied by a simple change in the law, or perhaps even through a presidential order changing OPM rules.

The insurance company proposed a $456 million rebate to the U.S. Treasury and another $289 million to be divided among current policyholders, since the premiums for federal employes are shared by the government and the individuals. Justice said the rebate to the government should be plowed back into the health insurance program to hold down premiums in the future or improve benefits.

OPM -- with the White House looking over its shoulder -- will decide whether the rebates will be made, and if so, to whom. It negotiates contracts for the federal health program, which covers all present and former U.S. workers from file clerks and CIA operatives to astronauts and members of Congress.

The civil service program covers more than 10 million people. More than half the people in the Washington area are covered by it. Blue Cross-Blue Shield is the largest of the more than 200 plans in the program.

The rebate proposal angered many other insurance companies. Some called it a "publicity stunt" designed to win more subscribers next year. No other plan has proposed a rebate.

At OPM hearings last month most of the other firms said any rebates should be returned to the health program to benefit all its members, not just Blue Cross-Blue Shield policyholders. Most of the firms have also experienced a drop in claims because of new emphasis on preventive health care and requirements that subscribers pay more of their medical and hospital bills.

Proposed refunds for white-collar workers would run from $73 for single policy-low option coverage to $374 for a policy with a high option-family plan. Postal workers would get refunds of $18 to $300 because the postal service pays a larger share of their premiums.