On June 30th the Michigan Freedom To Work Coalition came to life in a big way.
Around the state, multiple press conferences were held by union workers demanding the restoration of their freedom of association.
The freedom of association is not explicitely in the constitution, but as we know, the constitution lays out what rights the government has not what rights people have. We retain all our natural rights, dispite government and that means the freedom of association.
That said, the governments "acnowledgement" of the freedom of association can be traced back to a supreme court case. In 1958, the Supreme Court held in NAACP vs. Alabama that the freedom of association is an essential part of the Freedom of Speech because, in many cases, people can engage in effective speech only when they join with others.
Dispite that ruling the Wagner Act still strips workers of their choice to freely associate with a union or not associate with the union.
https://www.youtube.com/watch?v=f2q8wS8VkAE&feature=player_embedded