The Maryland General Assembly today approved a law requiring front-seat motorists to wear seat belts beginning July 1. The bill was sent to the governor, who is expected to sign it.

And in a House committee, another traditionally controversial measure, a bill to end the state tax break given the all-male Burning Tree Club in Bethesda, was approved. The committee delayed reporting the measure to the full House, however, after one of the bill's opponents raised constitutional questions.

Under the seat belt bill, approved by the Senate 29 to 17, a police officer could fine a motorist $25 for not wearing a belt, but only if the car had been stopped for a moving violation. The bill is one of the first major pieces of legislation to be approved during the three-month session, which ends Monday. A host of other bills, ranging from educational aid to the state's capital budget, remain deadlocked in joint House-Senate conference committees.

"I can't remember an end of the session with that many controversial issues still floating around," said Senate Budget and Taxation Committee Chairman Laurence Levitan (D-Montgomery).

House Speaker Benjamin L. Cardin (D-Baltimore), who will serve on two of the conference committees that have been appointed in recent days, said that the most "explosive" issues that remain to be resolved include state aid to education, the proposed Baltimore stadium authority, tax amnesty and the $220 million capital budget.

"This session has been remarkably free from election-year politics," he said. "So in the last few days you're going to see some frustrations."

Many of those frustrations have come from legislators who see their measures bottled up in committee as the adjournment approaches. Sen. Stewart Bainum (D-Montgomery) was both pleased with the Burning Tree Club bill's success in the full Senate and in the House committee and dismayed at what appears to be an ongoing fight to kill it.

Chief among its opponents is Del. Paul Weisengoff (D-Baltimore), who has orchestrated defeat for similar bills in previous years and once said of the issue: "The broads ain't in the pool yet."

Bainum and supporters of the bill called Weisengoff's protestations of constitutional problems a delaying tactic designed to gain enough time to ensure the measure's defeat on the floor of the House.

Weisengoff denied that he is assembling opposition to the bill, but said he does not like this year's version any better than previous ones. "I'm sorry they're so emotional," he said of the bill's supporters. "I don't think we should be in the business of breaking valid contracts."

The state's agreement with Burning Tree, whose members have included Vice President Bush and former presidents Richard M. Nixon and Gerald Ford, exempts the club from paying about $186,000 in taxes each year in exchange for maintaining much of its property as open space.

The House Constitutional and Administrative Law Committee also freed a bill today that had been languishing there that adds Maryland to a list of states that would participate in a southern regional primary in 1988. The southern primary is aimed at diluting the early influence of the New Hampshire primary and the Iowa caucuses in determining presidential front-runners.

The vote to approve the measure came after the committee had rejected it earlier in the day.

"This is a major step forward in trying to stabilize the presidential election process," said the committee's vice chairman, Del. Gerald Curran (D-Baltimore).

The measure passed out of committee on a 15-to-6 vote as supporters of the bill appealed to other legislators' border state sensibilities.

Another potential conflict also emerged late today when the Senate Budget and Taxation Committee voted to reject House Speaker Cardin's ambitious proposal to increase state aid to education by $335 million over six years, opting instead to support Gov. Harry Hughes' one-year $14 million plan.

Senate President Melvin A. Steinberg (D-Baltimore County) and Cardin will serve on the conference committee that will try to reach a compromise. Steinberg has said that Cardin's plan depends too much on future spending.

The House also approved a controversial measure today to allow insurance companies to continue setting their own rates without prior approval by Insurance Commissioner Edward J. Muhl. In an 82-to-46 vote, the House approved a version of the bill almost identical to one it rejected in January.

Opponents had said that providing for less, rather than more, regulation in the insurance industry at a time when 40 companies are on the state's watch list, is imprudent.