U.S. District Judge Harold H. Greene's decision to buck both the world's largest company and the U.S. government comes as no surprise to lawyers who have watched the judge closely during his 17 years on the bench.

Throughout his career, the 58-year-old judge has shown his feistiness and his determination to see that his view of justice is met, no matter how powerful the people before him or how much he agreed with the cause.

For example, despite his commitment to civil rights before he became a judge, Greene sentenced the Rev. Ralph David Abernathy to 20 days in jail in 1968 for violating federal assembly laws by leading a demonstration on Capitol Hill.

"I have no doubt you acted out of the highest principles and according to the dictates of your conscience," Greene said then. "But the enforcement of the law cannot depend on the justice of a cause or one man's conscience."

By refusing to dismiss the government's 8-year-old antitrust case against American Telephone & Telegraph Co. yes terday, Greene reiterated his commitment to the enforcement of justice, sharply criticizing lawyers on both sides for trying "to circumvent" legal procedures.

Although the judge did not object to a landmark AT&T divestiture plan drawn up to end the case, Greene criticized the way in which the settlement was filed, because the public would have no chance to formally comment on the agreement as is required by law.

Even before Greene took over the AT&T case 3 1/2 years ago, he had earned a high reputation as a legal scholar, with lawyers sometimes calling him "one of the best federal judges in the country."

His handling of the AT&T case has even further enhanced his reputation. Some communications lawyers credit Greene for the settlement, which requires AT&T to spin off about two-thirds of its assets into at least one completely separate local-service company.

In the face of skepticism by many antitrust lawyers that the AT&T case was too big and complicated to be tried, Greene proved otherwise.

Privately, he reportedly acknowledged that he had an unusual role in presiding over the case that sought to break up AT&T into several smaller companies. In an ideal world, he reportedly said, the future structure of such an important industry as telecommunications should be decided by social policy makers in the courts and Congress.

But since Congress and the administration didn't agree on a structure, and the case had come to him, he said he had a duty to prove that the courts could deal with the issues in an intelligent and prompt way.

Greene took over the case in June 1978 from a judge who was dying of cancer.

Within three months, Greene set a number of tight deadlines, developed innovative procedures to narrow the scope of the trial and began to push aggressively to bring the case to trial.

Last year, 48 hours after the trial began he agreed to recess the case for two months to give both sides a chance to complete a settlement -- but only after he was assured by both sides that a settlement was very close. Those talks failed and the trial resumed.

When the government completed its side of the case, and AT&T filed a motion to dismiss the suit on the ground the government had not proven its charges, Greene wrote a stinging opinion refusing AT&T's request. He said then that the government had presented a strong case showing violations of federal antitrust laws.

According to many communications and antitrust experts, that opinion, as well as Greene's promise to issue a verdict in the case by July, led AT&T to the bargaining table.

Greene's high reputation in Washington legal circles began during the early 1960's when, as to top Justice official, he played a crucial role in writing the Civil Rights Act. President Johnson apointed him as associate judge of the D. C. Superior Court in 1965 and chief judge in 1966. In 1978, he was appointed to the U.S. District Court.

Born in Germany in 1923, Greene left that country with his family in 1938 because, as he once said, "if you were Jewish and had a chance to get out, you did."

Despite Greene's frequently stern rebukes to lawyers in the AT&T case, lawyers on both sides respected him and clearly enjoyed working in his court. Not only was there an unusually high degree of camaraderie between AT&T and Justice Department officials but also there was a good rapport between the lawyers and the judge.

In one highly unusual event, both sides held a baseball game last spring in which they asked Greene to umpire. Having overseen enough battles in the courtroom, Greene declined that offer. But he did go to the picnic -- and proceeded to play volleyball, taking a turn on both teams to demonstrate his fairness and impartiality.