Freedom of Association/History/Noteworthy written sources
Is there another noteworthy written source from the past that mentions this right?
Pope Leo XIII forcefully argued for free association in Section 51 of Rerum novarum (1891) , an extremely influential text in Catholic thought.
"Private societies, then, although they exist within the body politic, and are severally part of the commonwealth, cannot nevertheless be absolutely, and as such, prohibited by public authority. For, to enter into a "society" of this kind is the natural right of man; and the State has for its office to protect natural rights, not to destroy them."