I apologize for not being able to answer that question directly, but what I can say is that while there may not have been any such legislation as such, it was certainly understood, as a kind of unwritten law.
I'm going to tell you a story. When I moved here, I had a neighbour who was francophone, but I didn't know it. I spoke to him in English and he answered in English. I eventually found out that he had moved here 20 years earlier, but that he had to hide the fact that he was francophone to avoid being treated as a second-class citizen. I've been here for 30 years now. That means that he had been reluctant to speak French for nearly 30 years.