Why did Comoros reject Mayotte’s decision to become a French overseas department?

Comoros rejects Mayotte’s status as a French overseas department because it maintains a long-standing territorial claim over the island, viewing it as an integral part of the Comoros archipelago.123

Following the 1975 declaration of independence by the three northern islands of the archipelago, the United Nations passed a resolution affirming the sovereignty of Comoros over the entire archipelago, including Mayotte. While the majority of Mayotte’s inhabitants chose to remain under French rule, Comoros and the African Union have consistently rejected the legitimacy of referendums—such as the 2009 vote that led to Mayotte becoming a French department in 2011—arguing that they violate the territorial integrity of the Comorian nation. This claim is symbolically represented by the fourth star on the flag of Comoros, which signifies the country's continued assertion of sovereignty over the island.1345