The 30-year-old firebrand, who did not attend the announcement of the verdict, was found guilty of three of the four charges brought against him, said Derek Hanekom, who headed a disciplinary hearing.
Malema was found guilty of disrupting a national ANC meeting and of bringing the party into disrepute by calling for regime change in democratic Botswana.
He was also found guilty of provoking serious divisions within the party by praising Thabo Mbeki, who was sacked as party leader and then ousted as South Africa’s president by the ANC three years ago.
“Ill-discipline is not a cure for frustration,” Hanekom said. “Such disobedience undermined the effectiveness of the ANC.”
Malema’s conduct “would have a negative impact on international and inter-state relations, and would be prejudicial to South Africa as a whole,” he added.
“In respects of the present disciplinary hearing, the respondent’s membership is suspended for five years,” he said.
“The respondant shall vacate his position as the president of the ANC Youth League,” he said.
Malema was, however, found not guilty of sowing racism or political intolerance.
The Youth League spokesman Floyd Shivambu was also suspended for three years over the Botswana statements as well as for swearing at a journalist, which the disciplinary hearing said had brought the party into disrepute.
Four other top Youth League officials were also found guilty on various charges, but were granted suspended sentences — meaning they retain their memberships unless they are convicted of a new offense.
The rulings mark a victory for President Jacob Zuma, who once used Malema to rally support for his campaign to remove Mbeki from power.
Malema, who once said he was ready to “kill” for Zuma, campaigned heavily for Zuma’s 2009 election. But in recent years, their relations have soured, with Malema repeatedly saying that Mbeki was a better leader against “imperialist” forces.
Last year, Malema was fined for “undermining” the ANC by saying that Zuma was worse than Mbeki, and warned that he would be suspended if convicted of a new offense.
Malema could appeal the sentence, a process that could take a year.
But analysts warned that Malema’s suspension from the ANC would do little to resolve the divisions within the party.
“In recent years, the ANC has become so divided and factionalized that it afforded ample political opportunity to the young and ambitious Malema,” said Fiona Forde, author of a new book about Malema.
“While Malema faces a harsh disciplinary sentence, the ANC must also take responsibility for the state of affairs that they have indulged. By and large, they have sat back these past three years and allowed this debacle to unfold,” she said.
“But beyond the ANC, South Africa’s socio-economic climate was also ideal for a man of Malema’s populist politics to emerge. The country is dangerously divided along social and economic lines.”
Steven Friedman, head of the centre for the study of democracy at Rhodes University, said that the faction of the ANC who backed Malema could easily find a new vehicle to express their populist views, on issues like nationalising mines, which Malema vocally supported.
“Malema is neither powerful nor popular. He owes his position not to massive support but to the fact that he is useful to one of the factions who are contesting for power in the ANC – the ‘nationalist’ or ‘populist’ group,” he wrote in the New Age newspaper.