The new legislation is the first overhaul of Angola's criminal code since it gained independence from Portugal in 1975.
President Rajoelina says he wants to reduce public spending.
He was arrested by the Amhara regional government at his residence in the capital, Addis Ababa
Oby Ezekwesili has pledged to form an opposition coalition to defeat the ruling party.
Evan Mawarire is charged with subverting the government and inciting public violence.
Mr Onnoghen has described the case instituted by the Code of Conduct Bureau as unconstitutional and lacking merit.
The signing was witnessed by senior leaders of Oromia, Oromo traditional leaders, elders, scholars, youths, and political party representatives.
The amnesty allowed pardons for people facing criminal or terrorism charges.
Expected to name his cabinet in the coming days
Officials have rejected the African Union's appeal