Kenyan citizens by birth who voluntarily renounced their Kenyan nationality when acquiring the citizenship of another country (in accordance with the repealed constitution), are entitled to regain their citizenship by applying in the prescribed manner. The procedure, undertaken by the Ministry of Immigration and Registration of Persons, may take a period of one year or more.
Kenyan citizens who hold dual citizenship and have renounced or lost their Kenyan citizenship at the age of twenty three (23) (in accordance with the repealed constitution), are automatically considered a Kenyan citizen by birth and may apply for citizenship in the prescribed manner.
Kenyan citizens who obtain the citizenship of another country are required to disclose their other (non-Kenyan) citizenship within three months of becoming a dual citizen. Failure to do so is an offence.
Source: immigration website