President Reagan's appointment of White House Counselor Edwin W. Meese III to succeed William French Smith as US Attorney General will have two important consequences. In the view of political observers here:
* It foreshadows a more assertive approach at the Justice Department and, if Mr. Reagan runs and is reelected, an even more vigorous effort to implement the President's agenda in such areas as affirmative action, prayer in the schools, and abortion.
* It seems to give White House Chief of Staff James A. Baker III unchallenged control of the presidential staff, now that his principal rival has been removed , and could help provide a more unified front at the White House as the President moves into the election year.
Legal experts say the staunchly conservative Mr. Meese will be a tough-minded , more ''hands on'' attorney general than was Mr. Smith, who resigned to return to his law practice. Meese has long talked about the job of attorney general, and the President may simply be rewarding him for loyal service. But by sending his forceful, articulate White House counselor into the Justice Department, the President is showing his concern about what happens in this crucial area.
''Because he knows the President's mind and has a more direct sense of what Reagan wants done, he'll be more aggressive in spearheading the social agenda,'' comments one legal authority. ''He'll go into Justice the way (James) Watt went into Interior - but without the latter's acerbic personality.''
Under the equally conservative Smith, the Justice Department has already moved appreciably to the right. It has revised the government's positions on antitrust law and civil-rights enforcement, asked the Supreme Court to reassess rulings on abortion, and tried to institute a system of secrecy oaths and censorship for government officials with access to intelligence data. It has also given high priority to investigation of violent crime and narcotics traffic.
On many social issues, however, the administration has been rebuffed by the Supreme Court. For instance, the court refused to give states and localities more say in regulating abortion. In the Bob Jones University case, it turned down the Justice Department's reversal of a long-standing government policy to deny tax-exempt status for schools that practice racial discrimination. And, most recently, it unanimously declined to hear a case involving affirmative-action hiring practices by the Detroit police force.
Inasmuch as the high court has not been responsive to the Reagan administration in these and other matters, it is believed that the President looks forward to altering the composition of the court. Four of the nine justices are over the age of 75, and if Reagan is reelected he could have an opportunity to fill one or two vacancies. Assuming he would make conservative appointments like Sandra Day O'Connor, this could have an impact on future judicial decisions in a conservative direction.
In addition to the Justice Department, the Meese nomination will have reverberations at the White House as well. White House officials say Meese's job as counselor to the President will not be filled, suggesting that the positions of Mr. Baker, Deputy Chief of Staff Michael K. Deaver, and staff secretary Richard G. Darman will be enhanced.
While it is too early to know how this will work out in practice, the expectation is the White House will be strengthened organizationally when Meese moves over to Justice. The past three years have been marked by frequent conflicts and tensions between the hard-line conservatives, represented by Meese , and the ''pragmatists'' or ''realists'' represented by Baker, Mr. Deaver, and others.
The battles may have arisen less over ideological differences than over tactics, strategy, and how to implement the President's policies. Meese, perhaps the closest to the President and unique in his ability to understand and advise him, is said to lack organizational ability and know-how to make the White House apparatus function smoothly.
Now that the domestic political program, including the State of the Union address and the 1985 budget, has basically been set, the White House priority is to concentrate on the reelection campaign. Therefore, Meese's departure is seen as potentially beneficial in an organizational sense. ''With Baker and Darman having more control over domestic policy questions, things will be better organized and there will be more precision,'' says one knowledgeable Reaganite. ''There will be more cohesion and unity at a time of political need.''
For Meese, appointment to a Cabinet post represents a step up from his already influential perch. And, despite his reputation for disorganization, Meese will take to his new job a record as a strong law-and-order enforcer. As deputy district attorney in California's Alameda County, he helped put down antidraft protests and moved vigorously against peace demonstrators at the University of California at Berkeley. In 1966 he joined Reagan's cabinet in Sacramento as legal secretary on clemency and extradition.
As counselor to the President, Meese has favored a ''guilty but mentally ill'' alternative to the insanity defense, spoken out against the ''exclusionary rule'' (which prohibits the introduction of illegally obtained evidence in court), and opposed busing and quotas to redress discrimination against minorities. He spearheaded the administration's drive against the Legal Services Corporation, which provides free legal assistance for the poor, and was instrumental in reshaping the US Commission on Civil Rights. Most recently he stirred a public furor when he questioned whether hunger in the United States is broad-based.
(From Capitol Hill, Monitor writer Julia Malone reports that congressional leaders see no obstacles blocking Meese's confirmation by the Senate. Sen. Robert C. Byrd (D) of West Virginia notes Meese's move could be a stepping stone to the US Supreme Court.)