Sir Ahmadu Bello, the Sardauna actually advocated for a secession clause in the 1959 constitution. Azikiwe was against it, backed by Britain the colonial, Zik who was speaking on behalf of he old Eastern Region got his way.
Now, 60 years later, the old east trying to renegade on the agreement
Excerpt: Zik Interview with New Nigeria in 1975
Again, however, when the 1954 constitution conference started, my good friend, Chief Obafemi Awolowo tabled a motion to the effect that in the new constitution, provision should be made that any state which feels like seceding should do so. I was opposed to it and said ‘no’ and said that once we have a federation, we are indivisible and perpetual. That was when we began to use that expression – ‘The Indivisibility and perpetuity of the federation’ – and that to secede would amount to treason. And so, a debate ensued.
The Secretary of State then was Oliver Littleton, later Lord Chandos and he was very much interested and that was his first time in seeing that people of African descent were people actually debating at a high level. So a full day was given to Chief Awolowo to make his points. He spoke brilliantly as a lawyer. He made his points why secession should be incorporated in the constitution. He cited the case of the Soviet Union which is a federation, and that secession is written there so that any state in the Soviet Union can secede at will.
He also cited the case of Western Australia and eventually he finished his case and was applauded. We adjourned. The next day, I had to reply. I availed myself of the opportunity to, well, demolish the arguments of my friend and I cited the case of United States which based its constitution on that of the Swiss Confederation. That is Switzerland. I pointed out a case, I think, that of Texas versus White, where Mr. Salmon Chase, the Chief Justice laid down the principle – he was really an arbiter – that the union was intended to be perpetual and indivisible and that any attempt to divide the union by secession was treasonable.
The North (NPC) supported Action Group. The question was then: Should we have secession? The Colonial Office came to our rescue. You know, the usual principle of Britain – ‘divide and rule’ (laughs) but this time, it was in our favour. So, the colonial office backed us. Lord Chandos said that on the face of the arguments before him it would be suicidal to incorporate secession in our constitution and that is why we have section 86 in our constitution that if any region or state should secede, then it will be an act of treason and that was what led to this war, because Col. Ojukwu seceded and so violated the constitution.