Just a year ago a group of liberal lawyers met clandestinely at the Park Hotel downtown to worry out loud about what they decribed as Shah Mohammad Reza Pahlavi's increasing violation of the judiciary's independence.

They were encouraged by President Carter's human rights stand and the persistent efforts by the likes of Amnesty International, the International Committee of the Red Cross and the International Commission of Jurists to pester the shah into ending the regime's worst excesses.

A year later, the dissident lawyers - and like-minded politicians, writers, professors and other westernized intellectual activists - find themselves under mounting attack from the government and overtaken - indeed thwarted by the mobilizing power of the Moslem opposition.

Stymied in efforts to persuade the shah to move gradually beyond his timid liberalization program, they readily concede their weakness and vulnerability.

They appear powerles to counter the shah's recent charges that their backing for a return to a less autocratic rule was all but tantamount to communist-inspired treason.

Their first priorities are their own survivial and preventing the threatened erosion of the few reforms the shah has granted.

"We must remain calm and give the shah no pretext for aresting - or taking legal action against us," a leading dissident lawyer said. "Silencing us would provoke no great public outcry - there are no more than 50 of us - unlike the ensured mass reaction if a religious leader were arrested."

Within the past month, lawyers and other dissidents have been subjected to bombs in homes and offices, telephoned threats on their lives and the lives of their families, beatings and a kidnaping.

Typical was the misadventure of Abdul Karim Lahidji, a lawyer who, along with 30 colleagues, in April successfully defended a group of 16 students arested during antigovernment demonstrations.

He has said he was jumped by six men upon emerging from a barber-shop April 27 and blackjacked into unconsciousness. His 12-year-old son ran back, alerted the barbershop customers. The customers scared off the assailants, who drove away in two cars without license plates - a favorite practice of SAVAK, as the Iranian secret police is called. The assailiants then apparently visited Lahidji's office and planted a bomb.

That kind of intimidation - and threatening telephone calls from a group calling itself "the Underground Organization for Revenge" - stopped during the early May visit of William Bulter, who heads the Geneva-based Internation Commission of Jurists.

Butler brought up cases of intimidation with the shah - as later the president of the Bar Association did with Prime Minister Jamshid Amouzegar. Dissidents reported that the telephoned threats resumed May 5, the day after Butler left Iran.

The dissidents also decry the presence of the Army - rather than the civilian police - on university campuses, city streets and in general riot control.

Yet, the dissidents make no secret of the undeniable relaxation of former restraints on their activities - a change many acknowledge may stem from their own ineffectiveness.

"Two years ago I wouldn't have dared meet you." Mehdi Bazargan, a veteran opposition political leader, told a correspondent. He stressed the importance of the foreign press in reporting on Iran - and the sensitivity of the regime to anything smacking of criticism.

But the limits on dissident activity are easily discernible.

What is known "Xerox literature" has flowered because of the regime's refusal to publish opposition communiques in the state-controlled press, much less allow dissidents to own or operate a press of their own.

Although only the Tudeh, or Iranian Communist Party, is officially banned, the shah appears to be in no mood to allow the formation of new political parties.

"No one even dares rent us a place to serve as headquarters for the Society for the Protection of Human Rights for fear of being bombed," writer Ali Ashgar Hadj-Seyed-Javadi said.

Dissidents are also depressed at their own inability to organize.

"For 25 years we have had no parties," Javadi said. "Iran has been in a state of siege and we have had no time to organize."

The Tehran dissidents are also disturbed by the violence of the religious protesters, especially against property belonging to minorities. Special targets have been Armenian-owned liquor stores or movie theaters, both considered sinful by religious Shia Moslems, and property owned by prominent members of the Bahai sect, including a soft-drink company and prominent bank.

Karim Sanjabi, a prominent moderate opposition politician, said "Violence and rioting is not in our interest and thwarts our efforts to advance toward a liberal regime. It only leads to worse dictatorship and revolution."

Many dissidents suspect that SAVAK has helped provoke such outrages in order to prove the government's point that the shah cannot relax his autocratic hold because the people are not ready for democracy.