From what I understand, they only have the right to ask where you live and why you are, where you are. They will probably send you home, if you shouldn't be where you are. Should you give them a rough time, they can ticket ($750 was mentioned by the solicitor general), or arrest you, if warranted. I suspect in this day and age, people will be indignant and announce their animosity on Twitter or similar.
Edited to add:
https://www.cbc.ca/news/health/ontario-covid-crisis-warnings-1.5991418