If is a legal requirement, you can definitely require it. I would spell out the requirement in your listing and when it is applicable. Then put in your house manual all of the information about your property that the tenant is going to need to give the insurance company and the steps that they need to go through to obtain, pay for, and receive proof of insurance.
This article in interesting because it says that most tenants do not have renter's insurance and near the end of the article says that it is NOT required. (see: http://www.cbc.ca/news/canada/ottawa/most-renters-skip-home-insurance-1.911039 )
Personally, I would not stay in an AirBnB that required it. I know that getting insurance will take at least a day, and if most of the other AirBnB listings did not require it, I might take that requirement in a solitary listing as a sign of an overly demanding, legalistic host.