What happens when a provincial government defies a federal law? We're about to find out

There's a big difference between an individual protesting climate change and a whole government not following a federal law.

The Liberals perhaps can't afford not to fight, but they could conceivably undercut themselves (and help Moe) if their response seems irrational.

This is precisely what Moe is counting on. The Liberals shot themselves in the foot when they tried to buy Atlantic Canadian votes by exempting heating oil from the carbon tax. That reenergized the opposition to carbon tax and gave the Conservatives a great stick to hit Trudeau with.

I hope the Liberals err on the side of public opinion caution and find a way to punish Moe's government without seeming draconian.

Legality has nothing to do with morality. People who think this are cop apologists and are probably the type to just follow orders in a fascist society.