What is the oldest written source in this country that mentions this right?
Antigua and Barbuda
In Antigua and Barbuda the 1981 constitutions second chapter offers a broad variety of protections. They range from the freedom of expression to the protection from discrimination on the grounds of race.
References:
“Republic of Antigua and Barbuda / República Del Antigua y Barbuda Constitution of 1981 Constituciones De 1981.” Antigua and Barbuda: Constitution, 1981: https://pdba.georgetown.edu/Constitutions/Antigua/antigua-barbuda.html.