The order was to expire on Monday but has now been prolonged until July 21.
There was a noisy but peaceful demonstration inside the downtown Universite du Quebec a Montreal campus when word emerged of the extension.
A few dozen masked protesters rushed into a pavilion just before noon and created enough noise to disrupt classes.
Later in the day, a group of several hundred held a protest against the Quebec government's austerity measures.
They marched through part of the city before heading for the university.
When they arrived, those inside had dispersed and the situation had returned to normal.
The second larger group also broke up and left when asked to do so by police.
The campus has witnessed several recent protests, including a few last week that resulted in more than 30 arrests.