There are enough grounds for the lawyer to fail in court. As much as the Nigerian constitution guarantees freedom of worship, the conduct of religious affairs lies in the power of the states to regulate.

If a part of Kwara State like the Ilorin Emirate has declared an official religion, in this case Islam, it will be impossible for the Federal law to override that. This same reason is why Sharia exists effectively till date in some states.

Igbale Aiye is not 450,000-yr-old. The age, according to Olofindji is 4,500 year. Here are the details of a visit to the place in 2013: https://www.africanartswithtaj.com/2013/02/igbale-aiye-where-souls-of-departed-rest.html

The distortion about "esin imole" was created as far back as many centuries to blackmail the early Yoruba Muslims. History of Islam in Yorubaland showed that Islam came from Mali, courtesy of the Turkish people who brought the religion then to most parts of sub-Saharan Africa. It was common among Yoruba traders then to pronounce Mali as 'Male' (even before Islam came to Yorubaland). This is a FACT! So, when most Yoruba started converting to Islam from traditional religion, it was natural for the religion to be called "esin Male" (religion from Mali). But later, when religious rivalry started creeping in between Yoruba Christians and Muslims, 'Male' became 'imole' as a response to Muslims calling Christians 'Kiriyo'.
So, there was nothing like "esin imole". It started from "esin Male (corrupted for Mali" and further corrupted to "imole."