THE PROPOSED federal criminal code arrived on the Senate floor last winter - after almost seven years in committee - with an unusual collection of friends and enemies. Leading the debate for it were two senators rarely found on the same side of any issue involving law enforcement and civil liberties: Edward M. Kennedy (D.Mass.) and Strom Thurmond (R.S.C.). Chief among its opponents were two senators with equally divergent views on such subjects, Alan Cranston (D-Calif.) and James B. Allen (D-Ala.). Those alliances tell you something. So does the final vote in the Senate (72 to 15). The code is neither the forward looking modernization of the criminal law sought by the Brown Commission in 1971 nor the repressive, vindictive legislation it was when it bore the designation S.l. It has evolved through compromises into a bill that leaves no one completely pleased but few totally distressed.

The mixed fellings of most critics leaves a House Judiciary subcommittee, which has just begun to mark up its version of the code, with something less than a free hand. It has an opportunity to make substantial improvements in this first general revision of the criminal law in the nation's history. But it must keep in mind the accommodations, so carefully negotiated in the Senate, that permitted the legislation to get this far.

It is almost impossible for anyone, other than the lawyers who have lived with it for a decade, to comprehend all of the changes this proposed code would make in federal criminal law. Almost everything from arrest procedures to sentences is touched by some provision in the 682 pages of the Senate bill. It would, for example, expand the civil rights laws, create a system to compensate victims of violent crime, increase the fines for white-collar crimes, practically eliminate parole from prison, repeal the Smith Act, make overseas corporate bribery a crime and modernize the sexual-assault laws.

The need for such a monumental legislative effort is one of the few things on which the bill's supporters and most of its opponents agree. The existing criminal law is a shambles - inconsistent, sometimes contradictory, scattered throughout the entire U.S. Code. This bill would pull it together, eliminate the inconsistencies and clarify what is left, while dropping such obsolete statutes as that making it a federal crime to detain a government carrier pigeon.

The most serious objection is the claim that it is a power grab by the federal government. Almost all of its opponents agree on that, even if they agree on little else. Sen. Cranston sees it as a serious threat to civil liberties because of the way it defines what crimes the federal government can prosecute. Sen. Allen sees that same characteristic as a serious attack on state's rights. Both say the bill would clear the way for a national police force and the federal courts to take over the investigation and prosecution of many crimes (for example, murder, robbery, assault, burglary) that have traditionally been left in the hands of local governments.

They have a point. In rationalizing all the statutes that Congress has passed in the last 50 years, the code does expand federal jurisdiction over some crimes, and it does give the sense of an enormous federal intrusion into ordinary law-enforcement activities. But the impression is illusory; much of this apparent new intrusion is old stuff; the new code simply calls attention to laws already on the books. The solution is not to try to rewrite the whole basis of the code now, as some of its opponents are urging, but to focus on this problem later. Some experience under the code will make it possible for Congress to know, for the first time, how widely it has cast the federal net in practise as well as in theory. Then it will have basis for a careful modification of the federal reach, if that seems advisable.

Apart from the united attack on that one aspect of the code, opposition to it is split. Some object to changes it does not make in the law. It does not, for example, re-institute the death penalty, modify the wiretapping laws or alter the changes Congress made a few year ago in the Supreme Court's Miranda rules and in the granting of immunity from prosecution. The code would be better if many of the proposals put forward in those areas by the American Civil Liberties Union were in it. But those parts of the existing law were left untouched in the Senate as the compromise to keep the bill from being destroyed by controversy. Our view is that even in areas like these, where major changes are badly needed, no change in the present law is better than no new criminal code.

There is also opposition, particularly from civil libertarians, to several provisions in the bill. The new code, for example, would fundamentally alter sentencing procedures in federal court and conditions under which prisoners are released. It may create problems for government workers who leak information to the press. Some of the changes it makes, especially those involving preventive detention and obscenity and conspiracy prosecutions, do create serious new threats to civil liberties. Those are specific issues to which we will return in a subsequent editorial.