Law scholar Prof Makau Mutua on Friday reignited his unending intellectual differences with Deputy President William Ruto, this time calling for revocation of his doctorate.

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Dr Ruto was among University of Nairobi students who graduated with doctorate in 2018 December, a move that ignited a national debate over the legitimacy.

And the Buffalo Law School Dean insisted that it's impossible for a person holding Deputy President seat to successfully complete a PhD without acquiring it fraudulently.

Makau Mutua now wants the DP's doctorate revoked and all those who supervised his thesis fired by the University of Nairobi.

"It’s impossible — a logical absurdity — that ANY sitting Deputy President can legitimately earn a doctorate," he said.

"Professors, supervisors, and university senate/council that passed, or awarded, the doctorate must be audited, investigated, and removed. Then the degree must be revoked," he added in reference to Ruto.

Dr Ruto submitted his thesis – titled ‘Influence of human activities on land use changes on environmental quality of riparian ecosystems: A case study of Saiwa Swamp watershed, Western Kenya’

He has graduated from the University of Nairobi with Zoology and Botany degree before pursuing Plant Ecology at both Masters and PhD level.

University of Dodoma lecturer Prof Amukowa Anangwe last year dismissed Ruto's achievements at 'political games' an indication that he too thinks it's not genuine.

“No wonder he has been deriding (Baringo County senator) Gideon Moi in rallies for being less educated than him. He will say the same thing against his opponents in the presidential race ahead of 2022,” says Prof Anangwe, who teaches at University of Dodoma, Tanzania.

Despite his milestone in a academics, Ruto is not however the first deputy head of state to get PhD. Josephat Karanja and George Saitoti all had doctorates.