His comments followed calls by McGill earlier this week for police to remove the dozens of tents that have been pitched on the field since Saturday in protest of the war in Gaza.
"The encampment is illegal," Legault told reporters in Quebec City. "The law must be respected, so I expect the police to dismantle these illegal campsites, which is what McGill has requested."
McGill's encampment is one of several across the country, including at the University of Ottawa and the University of British Columbia. Early Thursday morning, tents, banners and flags cropped up at the centre of the University of Toronto's downtown campus. Activists at all the sites are calling for their universities to cut ties with Israel.
Questioned about whether Legault's comment were appropriate, the federal justice minister suggested politicians shouldn't be telling police what to do.
"The operational decisions of the police are always theirs independently of politicians," Arif Virani told reporters in Ottawa. "This is always the case in a democracy like ours. … It sets us apart from other countries where the rule of law is not respected, so it's extremely important."
Meanwhile, Montreal police spokesman Jean-Pierre Brabant said Thursday the force is "still evaluating" the situation at McGill.
So far, he said, the encampment has been peaceful and it's not in the interests of the police or the city to immediately intervene.
At the protest site on Friday, pro-Israel and pro-Palestinian supporters held duelling demonstrations on either side of the fence at the main entrance to McGill, with dozens of police officers forming a line to ensure the two sides stayed apart.