When Attorney General Edwin Meese III addressed the American Bar Association last month, he criticized the Supreme Court for its recent decisions involving religion and states' rights.

Meese's prepared remarks bore a close resemblance -- down to the wording and order of cases he discussed -- to an analysis written a week earlier by Bruce Fein, a conservative legal analyst for the American Enterprise Institute.

Fein is part of a budding and influential cadre of conservative activists providing the intellectual underpinning for the Reagan administration's stances on busing, abortion, school prayer, crime and civil rights.

Such conservative organizations as the Free Congress Foundation, Washington Legal Foundation and Center for Judicial Studies are mounting an assault on traditional legal theory as a way of advancing longtime conservative goals. They appear to have a particularly aggressive ally in Meese.

"We're part of the team," said Patrick B. McGuigan, director of a judicial-revision project at the eight-year-old Free Congress Foundation. "We're trying to influence the agenda. We provide some of the intellectual power."

Terry H. Eastland, Meese's press secretary, said the groups are influential but do not call the shots at the Justice Department.

"It's not as though we have taken office and suddenly these groups are telling us what to do," he said. "I think the Justice Department's own postions in these cases really have not been shaped by the outside groups. I see them more as publicists engaging the debate in articles and on television . . . and also in the related industry of lobbying on the Hill."

The groups, many less than a decade old, have become a cottage industry that attempts to translate arcane legal theory into sweeping legal principles that can be easily digested and used by politicians, the news media and the public.

Nan Aron, director of the Alliance for Justice, a coalition of liberal groups, said liberal lobbies cannot approach the intellectual or political unity of the right. "We don't have a long list of foundations and institutes that churn out the reports," she said. "The primary reason is money; we don't have the resources."

Such groups as the American Civil Liberties Union and Leadership Conference on Civil Rights remain powerful political forces, although they now are often on the defensive. They also publish much material, but their focus tends to be on particular issues and cases, not broader legal changes that conservatives are championing.

"The strategy is to win the war, not a particular battle," said Fein, who worked in the Justice Department under then-Attorney General William French Smith. "The left is tactically oriented."

Fein appears to have been extraordinarily successful in bringing his ideas to the attention of the public -- through the office of the attorney general.

After the Supreme Court completed its term, Fein wrote that, in a case involving Grand Rapids, Mich., "the court nullified shared time and community education programs offered within sectarian schools" because they "unconstitutionally promoted religion in three ways."

Meese, in his analysis of the court's term, told the ABA that "the court nullified shared time and community education programs offered within parochial schools" because they "promoted religion in three ways."

The groups are riding a political wave that helped elect Ronald Reagan in 1980. With a conservative administration in place, their ideas were taken seriously, and they were sought by the media. Financial support quickly followed.

While old-line groups such as the American Enterprise Institute, which was founded in the 1940s, have focused on legal issues for many years, they have been joined by a new crop of energetic conservatives sophisticated in using the media and their own printing presses to make their case.

Some, such as the Washington Legal Foundation, are constantly going to court to counter liberal views and combat liberal politicians.

For instance, the foundation has argued successfully against appointment of an independent counsel to investigate the "Debategate" controversy over the Reagan campaign's acquisition of President Jimmy Carter's debate briefing books. It also won a case upholding the president's power to provide military aid to El Salvador despite congressional objections.

Former Interior Department trial lawyer Daniel J. Popeo began the Washington Legal Foundation in 1976 with a small bank loan, a one-room office, $100 in rented furniture and his wife typing at night.

It has grown to a $2 million operation in an N Street town house with a staff of 15 and nearly 200,000 dues-paying members and contributors. Conservative financiers Richard Mellon Scaife and Joseph Coors have been among the most important contributors to the group, which receives 40 percent of its money from foundations and corporations.

Unabashedly pro-business, Popeo churns out pamphlets on legal issues from natural-gas deregulation to "Judicial Politics Gone Wild" in Texas. He rarely turns down a chance to be "out in the trenches," as he calls it, carrying on the fight on television talk shows or in legal briefs.

The Free Congress Foundation, founded by New Right activist Paul M. Weyrich, has more than doubled in size in the past five years. Conservative Coors, the beer magnate, provides the largest portion of its $1.9 million budget.

When the group published a 1983 book on criminal justice reform, Meese and Smith were among the prime contributors. Its lobbying efforts also helped persuade Congress to adopt the Comprehensive Crime Control Act last year.

The foundation also monitors legal trends with a newsletter, Judicial Notice, which declared recently that "the left's monopoly on the legal policy debate has ended . . . . The left's various legal groups use the judicial process to secure victories not obtainable through the ballot box."

The two-year-old Center for Judicial Studies in Cumberland, Va., promotes constitutional theories similar to the "strict construction" approach espoused by conservatives in the late 1960s.

James McClellan, a law professor, former aide to archconservative Sen. Jesse Helms (R-N.C.) and former chief counsel to the Senate Judiciary Committee, said the center is geared to reining in an activist and liberal-dominated federal judiciary and countering liberal views in the American Bar Association and in law schools.

The small center publishes an increasingly influential bimonthly magazine called Benchmark, distributed to all members of the federal judiciary, state supreme courts and Congress as well as to the news media and law schools.

"We don't litigate," McClellan said. "Our real opponents are sitting on the bench or on the campuses."

Like other conservative publications -- and unlike law school journals -- Benchmark is "deliberately written in laymen's terms" to appeal to nonlawyers, McClellan said.

These groups, along with kindred spirits in the nation's law schools, provide more than just ideas for the administration.

Legal scholar Marshall Bregar left the Heritage Foundation two years ago to join the White House staff. Harvard Law School professor Charles Fried is now acting solicitor general, and University of Texas professor Grover Rees III, formerly on McClellan's advisory board, is on Meese's staff and in line for a key Justice Department assignment.

The new groups share a common objective of packing the federal bench with conservatives and monitoring those already named by Reagan, who will likely have appointed more than half of the nation's federal judges by the end of his second term. Their publications provide a forum for those judges to expound on the right's agenda.

Conservative think tanks have not been disappointed in Meese. They led the cheering when he approved a brief in which the Justice Department for the first time asked the Supreme Court to overturn its 1973 decision, Roe v. Wade, that legalized abortion.

Eastland said Meese has not broken with past policy on this and other issues, adding that the abortion brief was written by veteran department lawyers. He acknowledged, however, that "people know Meese is a little bit more aggressive than his predecessor and they may be more encouraged to take a stronger position."

Aron said she was not surprised by the move, noting that the conservative groups "have a direct line to Ed Meese. They are part of his network. The decision to try to overturn Roe v. Wade is prime evidence of . . . who is giving him his signals."