In Canada magazines are classified according to capacity and what they are designed and manufactured for. Not the weapon in which they are used. By law, pistol magazines can contain up to 10 rounds, semi-automatic rifle magazines can contain up to 5 rounds.

The Tavor is shipped with a 30 rounds magazine pinned to 5 rounds (on the left).

Tavor magazines

What if you find a pistol magazine that works in a semi-automatic rifle? It is legal since the magazine was designed and manufactured for pistol use. How you use it is irrelevant, it's classification does not include it's usage!

So this is why I can use 10 rounds magazines in my Tavor (on the right). BUT it has to be that particular model only (I added a Tactipul Floorplate to it).

Pistol magazine

Note that these magazines can be used in any AR-15 compatible rifle.

Links to detailed explanations: PDF    Legal ruling