The e-toll project in Gauteng must be put on hold with immediate effect, Judge Bill Prinsloo ruled in the High Court in Pretoria on Saturday.
"I make the following order… the first respondent [SA National Roads Agency] is interdicted and restrained from levying and collecting tolls," said Prinsloo.
Everyone in the public gallery stood up and clapped hands after he delivered his judgment.
Prinsloo granted an urgent interdict, brought by the Opposition to Urban Tolling Alliance (Outa), to stop the launch of the system, so that a full court review could be carried out to decide if it should be scrapped or not.
Prinsloo said that while he realised Sanral would suffer huge financial losses, members of the public would also suffer hardship of the controversial project went ahead.
E-tolling was to have been implemented on the 185km of highway in Gauteng on Monday April 30.
In a statement on Thursday night, the transport department said its implementation was being postponed until May 30.
This was to "finalise regulations following input on regulatory and administrative issues from the public and interested stakeholders".
Welcoming the decision, the ANC said it showed leadership and responsiveness by the government.
"It is encouraging to us that we live in a democracy where these issues can be thoroughly debated and discussed," added Cosatu spokesman Patrick Craven.
Cosatu has postponed a general strike against e-tolling planned for Monday.
The delay would give it time to assess the success of resistance to e-tolling, and any future legal action.
Other mass action planned for Monday, including a highway blockade in Johannesburg, would go ahead, Vavi said.