The Constitutional Court dispensed with the High Court's limitation of its order to the use, cultivation or possession of cannabis "at home or in a private dwelling".
Deputy Chief Justice Raymond Zondo has upheld an earlier high court judgment.
He added that it would not be a criminal offence for an adult person to use or be in possession of cannabis in private for their personal consumption in private.
Pro-marijuana activists cheered in the public gallery and chanted "Weed are free now" when the Constitutional Court gave its landmark ruling.
The state, however, believes that it is not in line with the Constitution, as cannabis is more harmful to users than tobacco and alcohol.
This also extended to cultivating cannabis in a private place for personal consumption in private.
Prince argued that the criminalisation of dagga use and possession was a violation of the right to equality, dignity, and freedom of religion. We still believe there are over 600 arrests for cannabis use.
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Jeremy Acton, the leader of the Dagga Party, which campaigns for the use of cannabis, said the ruling should have gone further to legalise the carrying of marijuana in public.
But ultimately, it would be up to the court to decide whether the person in possession of cannabis had the intent to deal it, or use it for his/her consumption.
Cannabis is referred to as "dagga" in South Africa.
"We are looking forward to telling the police to leave us alone now", said Clarke on the decriminalisation of private use.
Zondo said that this reading-in will apply until such time as Parliament fixes the Constitutional defect in the case.
In April Zimbabwe became the second country in Africa, after Lesotho, to legalise the use of marijuana for medical use.