Eastern tigers are federally protected, which means you can't touch the native eastern tigers. If you can possess tigers otherwise, then your only obstacle is whether they are legal in Saskatchewan [which may depend on species and subspecies]. I don't know Saskatchewan laws, but it comes down to this: if Saskatchewan treats the animals as a native form AND prohibits collection/sale/possession of native forms, then you shouldn't get them. That would be a violation of WAPPRIITA. If they don't protect native tigers, or the animals aren't defined as native, you're likely fine, assuming you're spot-on about ON laws.
Odds favor that last sentence. Check the HISS forums for Saskatchewan legalities.
In Alberta, all tigers are legal, native or otherwise. All protected Alberta species are illegal to possess, regardless of origin.
Federal law in Canada: Eastern tigers and BC blotched tigers are federally protected [SARA], so obtaining native animals from either of these places would be a violation of federal law. Likewise, obtaining them illegally from anywhere in the world is a federal violation [WAPPRIITA], though that could be difficult to establish [like the situation with Lurestan mountain newts].
Ontario law: lots of municipal by-laws to confirm, though you're likely safe, and many such laws are seldom enforced.
Native eastern tigers are protected, though I don't know how Ontario law deals with exotic specimens. You should double check exactly what the law says about tigers, as there are many species.
Also check the health laws. Odds are, you're safe here as well, since aquatic turtles are commonly sold in Ontario [and they tend to be a bigger concern]. Eg. - in Alberta, a number of turtles are legal to possess under the wildlife regulations, but the communicable disease regulations prohibit sale and import of a bunch of those.