Freedom of Association: Country sources - Djibouti

What is the oldest written source in this country that mentions this right?

Article 15 of the 1992 Constitution of the Republic of Djibouti guarantees both freedom of association and the right to strike.

References:

1992 Constitution of the Republic of Djibouti: "Title I: Of the State and Of Sovereignty," Constitution of the Republic of Djibouti, 15 September 1992 : 3-4 https://heinonline-org.proxygw.wrlc.org/HOL/Page?collection=cow&handle=hein.cow/zzdj0005&id=3&men_tab=srchresults