The Oyo Mesi was the legislative arm of the Oyo Kingdom

The Oyo Mesi were seven principal councilors of the state. They constituted the Electoral Council and possessed legislative powers, similar to today's United States Congress  led by the Bashorun, acting as prime minister,and ran by the Agbaakin, Samu, Alapini, Laguna, Akinikuand Ashipa.


They represented the voice of the nation and had the chief responsibility of protecting the interests of the empire. The Alaafin was required to take counsel with them whenever any important matter affecting the state
occurs. Each man had a state duty to perform at court every morning and afternoon. Each mesi had a deputy whom they would send to the Alaafin if his absence was unavoidable.
The Oyo Mesi developed as a check on the Alaafin's power, preventing the Alaafin from being an autocrat; the Oyo Mesi compelled many Alaafin to commit suicide during the 17th and 18th centuries. The head of the council of Oyo Mesi, the Bashorun, consulted the Ifa oracle for approval from the gods. New alaafins of Oyo were seen as appointed by the gods. They were regarded as Ekeji Orisa, meaning "companion of the gods." The Bashorun had final say on the nomination of the new Alaafin, his power rivaling the king himself.


For example, the Bashorun orchestrated many religious festivals; in addition to being commander-in-chief of the army, which gave him considerable independent religious authority. Chief among the responsibilities of the Bashorun was the all important festival of Orun. This religious divination, held every year, was to determine if the members of the Mesi still held favor with the Alaafin. If the council decided on the disapproval of the Alaafin, the Bashorun presented the Alaafin with an empty calabash, or parrot's egg as a sign that he must commit suicide.


This was the only way to remove the Alaafin because he could not be legally deposed. Once given the parrot's egg, the Bashorun would
proclaim, "the gods reject you, the people reject you, the earth rejects you." The Alaafin, his eldest son, and the Samu, his personal counselor and a member of the Oyo Mesi, the Asamu, all had to commit suicide in order to renew the government all together. The process and suicide ceremony took place during the Orun festival.


The Ogboni


The Oyo Mesi does not enjoy an absolute power or influence, and while the Oyo Mesi may wield political influence, the Ogboni represented the popular opinion backed by the authority of religion, and therefore the view of the Oyo Mesi could be moderated by the Ogboni. And most interestingly, there are checks and balances on the power of the Alafin and the Oyo Mesi and thus no one is. arrogated absolute power. The Ogboni was a very powerful secret society composed of freemen noted for their age, wisdom and importance in religious and political affairs. Its members enjoyed immense power over the common people due to their religious station. A testament to how widespread the institution was is the fact that there were Ogboni councils at nearly all sub-courts within Yorubaland.


Aside from their duties in respect to the worship of the earth, they were responsible for judging any case dealing with the spilling of blood. The leader of the Ogboni, the Oluwo, had the unqualified right of direct access to the Alaafin of Oyo on any matter.

Source : The Alaafin of Oyo