Mart Niklus was awestruck when speakers at a conference blessed by the Kremlin made the same statements that had landed him in prison, but he said the new freedom had not penetrated Soviet labor camps. Niklus, a dissident for decades who was freed July 8, heard two days of speeches as a guest delegate to an officially sanctioned meeting of the People's Front, an Estonian nationalist group. ``A lot has changed,'' he said. ``People have become less afraid of publicity. They criticize the authorities boldly. ``People are more frank, open-hearted. National self-consciousness has become very strong. It's surprising for me.'' Niklus agreed that fewer people are going to jail for political reasons, but also said the reform program President Mikhail S. Gorbachev calls perestroika had not eased the misery of those already there. ``There have been no changes. Perestroika hasn't reached the correctional labor camps,'' he said. For Niklus, the memories of arrests and prison are too vivid to permit complete belief in Gorbachev's reforms. He still holds his hand over his mouth when speaking of politically sensitive matters. As a reminder to all, the 54-year-old former inmate wore the black-and-gray striped uniform of ``special regime'' prisoners like himself who are repeat offenders or considered especially dangerous. Speakers at the conference Oct. 1-2 in Tallinn's city hall urged Moscow to renounce Josef Stalin's pact with the Nazis under which the Soviet Union took control of independent Estonia, Latvia and Lithuania in 1940. ``I was sentenced for that. ... I got 10 years for that,'' Niklus said in the excellent English he learned while studying ornithology before he was sent to prison. He and 47 other activists signed an appeal on the 40th anniversary of the agreement, Aug. 23, 1979, demanding its renunciation. He was arrested in April 1980 on charges of ``anti-Soviet propaganda and agitation'' and sentenced to 10 years in prison and five in internal exile. It was Niklus' fourth arrest. He spent eight years in jail in the 1960s. Now even the Estonian Communist Party is calling for a review of Stalin's foreign and domestic policies. The party also has taken up some of nationalist demands: making Estonian the official language, gaining local control over the republic's economy and curbing immigration of non-Estonians. As a ``special regime'' prisoner, Niklus spent most of his time in solitary. He was hospitalized for a month after his release, being treated for chronic back pain that developed because he was forced to sit for long periods and poor eyesight he said resulted from confinement in a small, dark cell. To illustrate the decline of his health, Niklus displayed two photographs _ one taken in 1976, before his latest imprisonment, in which he had a full head of black hair and full cheeks; the other taken after his release in July, showing a man with gray, thin hair and sunken cheeks. ``You are not treated as a human'' in special regime, he said. Niklus described the standard diet was thin gruel, bread and weak tea with sugar for breakfast; cabbage soup, bread and oatmeal for lunch, except for Sunday when the main course was macaroni, and hot water and a small piece of fish in the evening. Those meager rations may improve, however. On July 25, the Soviet parliament directed that rations for prisoners in solitary confinement or special regime no longer be reduced. Western estimates put the number of Soviet labor camps at more than 1,000 and say they hold at least 1 million people, perhaps twice that. Amnesty International, the London-based human rights group, says about 200 people now are in labor camps, psychiatric hospitals or internal exile because of political beliefs, compared with 10,000 a few years ago. Soviet officials say all but a few people classified in the West as political prisoners were freed by amnesties in February and June 1987. They say the ``anti-Soviet propanganda and agitation'' law under which they and Niklus were convicted is being softened in a revision of the criminal code. Perhaps, but Niklus said: ``They may arrest me again now. I have been arrested four times. You never know when they will get you again.'' Then he added, with a slight chuckle: ``But I am not afraid. I have a kind of immunity.''