Translating to "Long Live Free Quebec", it is considered by many to be Charles de Gaulle's semi-formal endorsement of the concept of Quebec sovereignty.
In the aftermath, Charles de Gaulle was forced to cut his visit short partially due to the outrage of the Canadian government at this statement. Since then, it has been a rallying call for supporters of Quebec sovereignty, as well as the Parti Quebecois, a pro-sovereignty political party based in Quebec.
It is widely believed that because of animosity stemming from this incident, then-Canadian Prime Minister Pierre Trudeau refused to attend a memorial service to Charles de Gaulle following his death some years later.
Crowd: *goes apeshit*
Parti Quebecois Member#1: "Je te vois a la prochaine assemblee. Vive le Quebec Libre!"
Parti Quebecois Member #2: "Je te vois la aussi, et Vive le Quebec Libre!"