The line began forming before 7 a.m. today as it does every weekday outside the cluttered downtown office of the Black Sash civil rights organization. By 8, nearly 50 blacks were waiting for legal aid in dodging South Africa's intricate governmental machinery that exiles those without the right papers to distant rural areas far from jobs and a viable living.

But there was an atmosphere of quiet elation among staff workers here this morning, and a new hope that by this time next year the line outside this office may be diminished. It followed indications that the white-minority government was planning to restore black citizenship and considering the abolition of restrictions such as passbooks on black movement.

These changes would not alter many of the fundamentals of the apartheid system of racial segregation nor necessarily dilute white control. Blacks still would be disenfranchised nationally and unable to live or attend schools outside strictly segregated areas.

But the changes would affect some of the most restrictive aspects of apartheid, and Black Sash leaders said they could amount to an important victory.

"Although there's a long way to go, this really is a cause for hope for South Africa's future," said Black Sash President Sheena Duncan.

Others were less certain, puzzling over the various conditional clauses in yesterday's citizenship statement by South African President Pieter W. Botha and today's report, which had been anticipated here, on "influx control" by a committee that advises Botha. Blacks appeared to be the most suspicious.

"I'm very skeptical," said Sy Molotse, a young black volunteer. "There's nothing to be excited about, because many promises have been made before and broken."

Beulah Rollnick has given legal aid since 1978 to some of the 15,000 blacks who come to this office each year seeking help. "I write affidavits in my sleep," she said, adding that abolition of influx control would not stop police raids on blacks living illegally in white areas.

Residential segregation is maintained by a different law, the Group Areas Act, which the government has promised its white constituents it will maintain.

But abolition of the passbook controls would affect hundreds of thousands of blacks like Ndabakayise Luthuli, 43, a well-dressed, unemployed construction worker who currently faces expulsion to his black "homeland" of KwaZulu after spending 24 years working in "white" cities such as Johannesburg.

His story illustrates the intricacies of the legal system South Africa has erected to control the movement of its black majority -- a system that Duncan and Rollnick say now may start to be dismantled.

Like his father before him, Luthuli left his family and came to Johannesburg in 1961 for work because, as he put it, "there is no employment, absolutely nothing" in the remote rural area of Nongoma, where he was born and raised.

To get here, he applied to a labor bureau in KwaZulu that found him a job, signed him to a one-year contract and authorized him to travel. He was not allowed to come to Johannesburg to seek work himself.

When Luthuli arrived, his company sent him to the local "development board," which issued him a passbook allowing him to remain in the area and placed him in an all-male hostel in the all-black city of Soweto. Because he was only considered a temporary sojourner, Luthuli's wife and seven children were required to remain in Nongoma, 250 miles away. He said he sends them about $40 per month.

It is a precarious and lonely existence. Luthuli must carry his dog-eared passbook with him everywhere or risk arrest and a fine. In it, his citizenship is recorded as KwaZulu, not South African, and he can be returned for any offense.

Each year at the end of his contract, Luthuli must return to Nongoma and reapply to work in Johannesburg. He said he has not been home for the birth of any of his children and he remains a stranger to them, just as his father was to him.

Recently Luthuli was laid off in the middle of a contract. Blacks who remain in one white area or work for one employer for 10 years or longer qualify for permanent residential status, but as a construction worker Luthuli often has switched jobs and locales. Without his job, he has no legal right to remain in Johannesburg for more than 72 hours.

If the government follows through on the recommendations of Botha's advisers, both the influx control act and the pass laws will be scrapped. Luthuli no longer would need a passbook to remain in Soweto. Provided that he could find a house, he also would be able to bring his family to Soweto to live with him. He would be issued an identity card like that of the whites, and it would record his citizenship as South African.

Duncan, who has been president of the Black Sash for 10 years, succeeded her mother, who helped found the group. She has a reputation for realism. Apartheid will remain until the Group Areas Act and the racially based national constitution are scrapped, she said.

Nonetheless, she said she cannot help but be hopeful that the moves announced this week will prove to be a major turning point. "I do not believe that having got this far, he Botha can go back on it," she said. "Once you've said everybody can be South African again and they can move where they want to, it changes the whole situation."

She turned to blacks awaiting advice. "The pass laws must go," she said. "No more reference books, no more stamps in your passbook. It's the first real sign that apartheid is being dismantled." There was an audible sigh from the group.

"I could actually burst in tears . . . because it has been so many years of misery and suffering," said Duncan, who then began to cry. "It's just great."