It's legal in Alberta so long as:
- The first trailer is a fifth wheel
- The first trailer has two or more axles
- The first trailer is the longer trailer
- The hitch for the second trailer needs to be attached to the frame of the first
- Whole setup can't exceed 20m (from front of the truck to back of the second trailer)
If you thinking of doing what I think you are (towing a ZJ on a car hauler behind a travel trailer), be careful and have the trailer and ZJ weighed together. My ZJ with mods is sitting at probably 5500lbs and the whole towed assembly would be sitting closer to 7500lbs once on the trailer. With the length restriction, you're looking at probably a maximum length of 16' for the car hauler (less depending on the truck length).
The folks who run the weigh scales would be the ones who would know exactly, since they'd be the ones who would be seeing your setup a lot.