Mr. Libman was an elector in Quebec during the 1992 referendum, which was governed by Quebec legislation. He argued that the mandatory requirement, under the Quebec legislation, that he had to be part of an umbrella committee on either side infringed upon his freedom of expression and his freedom of association. After fulsome consideration, the Supreme Court ruled that his individual right to freedom of expression and freedom of association was infringed upon by the provisions in the legislation.
I'm not familiar with all that followed, but I believe that Quebec's Referendum Act was amended afterwards to factor in the consideration of the Supreme Court.