Issues of sub-national referendums regulated at the national level

Political Constitution of Panama(Constitución Política de la República de Panam?).

https://www.constituteproject.org/constitution/Panama_2004.pdf

Article 238

By popularinitiative and through the vote of the respective Councils, two or moremunicipalities may

request theirincorporation into a single one, or into an association, for reasons of commonbenefit.

Correspondingprocedures shall be established by law.

The municipalitiesof a province with like requisites may unify their regime, establishing acommon

treasury andfiscal administration. In this case there may be created an Inter-MunicipalCouncil

whose compositionshall be determined by law.