Unfortunately, it's no longer possible to simply read the constitution to fully understand the rights afforded to an individual. The US Supreme Court has long upheld that a person has more fundamental rights than are explicitly enumerated in The Constitution.

Technically speaking, persons always had a freedom of association, but the court made it explicit during N.A.A.C.P. v. ALABAMA [1].

[1] http://caselaw.findlaw.com/us-supreme-court/357/449.html