FIVE YEARS AGO Sen. Edward M. Kennedy (D-Mass.) mused during a long plane ride about how much power the chairman of the Senate Judiciary Committee has to do good for the American people.

At that time Kennedy was fifth in seniority on the committee and -- then as now -- a possible presidential candidate. He showed the full potential of the Judiciary Committee by using the power of his subcommittee chairmanships to lead the charge into such diverse areas as Watergate, foreign policy (the Vietnam war and Bangladesh), big business and monopoly, gun control and government secrecy.

Now Kennedy holds most of the marbles as the new chairman of the Senate Judiciary Committee, but this new responsibility appears to have dampened his enthusiasm for groundbreaking moves -- opposed by big business -- against white collar crime.

A key aide, Kenneth Feinberg, revealed that Kennedy plans to scrap parts of his criminal code reform bill opposed by big business that would extend criminal prosecution directly to corporate executives if their companies disobey federal laws. As the law now stands, only the corporation -- not the executives who run it -- is criminally liable.

"We are taking into account some of the concerns of the business community and are altering the code to meet those concerns," Feinberg said.

Under last year's Kennedy-sponsored, Senatepassed bill, corporate officials would face criminal charges if their company failed to obey U.S. laws in such areas as security regulation or environmental protection.

The executives would not even have to disobey the law intentionally. Just failing to exercise the leadership expected from top corporate executives would have been enough to bring criminal charges.

This, Feinberg said, would have been a major expansion of federal controls over corporate conduct -- something critics of the current law think is badly needed. It will be dropped.

Kennedy said last week he can see making executives of pharmaceutical companies criminally liable, as they now are under U.S. food and drug laws, when their companies fail to follow the law because that is a matter of health and safety.

But, the new committee chairman said, he does not feel the same way about other kinds of corporations since the federal laws governing them deal with economic matters.

Besides changing the bill to meet business objections, Feinberg said, Kennedy is revising it to meet the complaints of the House, which thought the Senate version went too far in its omnibus attempt to reform the federal criminal code.

In other areas under the jurisdiction of the Judiciary Committee, Kennedy plans to push a bill to speed up vast antitrust cases, such as the suit against IBM, which has been dragging through the courts for 10 years.

Joel Perwin, who is handling antitrust matters for Kennedy, said the committee may want to look into American Express' attempt to take over McGraw Hill Publishing Co. in terms of its First Amendment implications and the question of the responsibilities of American Express President Roger H. Moreley, who also served as a McGraw Hill director before the merger offer.

Kennedy also wants to push the committee in a new direction -- the first systematic look at the way the nation's entire legal system works to see if there are ways to make it easier and cheaper for ordinary citizens to get their problems handled.

"The cost of litigation and the time it takes to get a case settled is an increasing matter of concern," Kennedy said.

"We have increasing skepticism about the system among Americans, who are questioning whether it is usable. This means an increasing lack of confidence if it continues to develop and has adverse implications for the rule of law in the country."

When then-Congressman Robert L. F. Sikes (D-Fla.) was called before the House Committee on Standards of Official Conduct (ethics committee) in 1976 on conflict of interest charges, he thought Lawrence Hogan would be just the lawyer to represent him. Hogan, then in private practice with his wife, Ilona, and now the newly elected Prince George's County executive, had been a congressman himself.

"He would be familar with congressional procedures, with the workings of congressional committees and knowing most of the principals involved, the members of the House ethics committee, would have an understanding of the ways in which to best represent me," said Sikes.

As so often happens between lawyer and clients, differences developed. Sikes felt Hogan was not getting his story acors to the ethics committee, whose staff "appeared to be pushing Mr. Hogan along."

Now Lawrence and Ilona Hogan are suing Sikes for $16,740 in legal fees on top of the $12,030 he already paid them.

Among other things, Sikes complained that he did not think Mrs. Hogan would be representing him along with her husband and that he did not know Hogan was charging $100 for every hour he worked on the case -- including eight fruitless hours standing outside the ethics committee waiting to argue on Sikes' behalf.

Pretrial papers filed with U.S. District Court here showed the Hogans' firm income -- $100,000 in 1975 and $130,000 in 1976. Hogan now makes $51,600 as Prince George's executive.

Not too long ago Walter Flowers (D-Ala.) was the Southern conscience of the House Judiciary Committee's impeachment of President Nixon. When he saw the smoking gun, everyone knew Nixon was through.

Now Flowers, retired from Congress, has become a partner in the Washington law firm of Collier, Shannon, Rill, Edwards & Scott, where he will specialize in the same issues he handled in Congress -- antitrust, energy, the environment and research and development.

As a congressman, his Birmingham district contained some of the biggest steel industry polluters in the country. He said the clean air act is good, "but maybe some fine tuning is needed for energy and economic needs."

Flowers said he stands ready to help with that fine tuning as a consultant, lobbyist or lawyer -- "They're all mixed up in this town."