Miguna revealed the development on Saturday morning terming it as a cowardly move.
He said Raila's move will not cloud the planned release of his new book "TREASON: The Case Against Tyrants and Renegades".
"It's going to be an explosive revolutionary engagement ahead," he tweeted on Saturday. Miguna's relationship with Raila deteriorated following his February 6 deportation for taking part in the ODM leader's mock swearing-in as the People's President on January 30.
The self-declared NRMKe leader was denied entry into the country on March 26 after he refused to apply for a visa that grants him legal stay in Kenya.
After he was forced to leave for Canada, Miguna accused the NASA leader of not coming to his help by failing to secure his freedom.
Miguna, who vied for Nairobi governor in August 2017, has also expressed displeasure with the March 9 handshake between Raila and President Uhuru Kenyatta.
He described it as betrayal by Raila. The ODM leader's move ended the revolt that followed the disputed 2017 presidential election.
While he has been vocal about the relationship, Raila has not publicly spoken of the issue.
The lawyer also published a book 'Peeling back the mask' in 2011 where he criticised the ODM boss.
Miguna wrote the book after he was relieved of his duties as Raila's adviser when the latter was Prime Minister.