Article 2 of the 15 February 1959 Constitution of the Republic of Dahomey guaranteed freedom of association, though in the context of respecting public order.

Freedom of association in the Republic of Benin was also guaranteed in the Constitution of Benin that was adopted at the referendum on December 2nd, 1990 under Title II, article 25

References:

"Of the State and of Sovereignty," Republique du Dahomey, Constitution du 15 fevrier 1959 (1959): 57-57: https://heinonline-org.proxygw.wrlc.org/HOL/Page?handle=hein.cow/zzbj0032&id=3&collection=cow&index=#

1990 Constitution of the Republic of Benin: https://constitutionnet.org/sites/default/files/Benin%20Constitution%20-%20English%20Summary.pdf