The last time Royal Assent was refused in Canada was in the province of PEI in the 1940s. The Government passed a bill repealing prohibition. The Lieutenant Governor personally favoured prohibition and he refused Royal Assent.
Fascinating! Thank you (and Malden) for that. I had no idea Canada even had prohibition, much less that it was a thing in places until the 1940s. This place definitely is educational. 
And in the end, the test of checks and balances is whether they *work *to prevent thigs going off the rails, and it all depends on the players continuing to agree on the legitimacy of the social-political contract, that playing by its rules is beneficial while overthrowing it would be deleterious. Lose *that *and it matters not if the branches are seen as mutually adversarial walled gardens, there’s a history of three-separate-branch presidential republics right in my back yard becoming the fief of one ruling faction, when people stop feeling those in power need to beseech support and start feeling they’re owed obedience. Same as with there being a written vs. unwritten constitution – the world is littered with hundreds of expertly well-drafted, referenced, annotated constitutions and charters that became (or were from the start) not worth the paper they were printed on.
You Burkeian! 
As seen recently with South Korea, the president can be impeached by the unicameral parliament; however, that alone does not eject him or her from office. The Constitutional Court of Korea has to approve the removal from office.
The South Korean president has a few interesting constitutional powers, one of which is “suspending all laws or enacting a state of martial law”. The parliament can overturn the president’s decisions.