I suppose in Mr. Edward's case, it's not so much a legal argument as a moral one. He's choosing to withdraw his tax support from the country that facilitated his making his fortune in the first place, and instead paying taxes into a country that really did nothing to earn it. I'm sure it's a matter of principle to him, it's just that the integrity of that principle is questionable at best.
My take is that Mr. Edwards has no moral conundrum to face on this issue in any way, shape or form. In my eyes, it's quite the opposite really in that gubmint needs to start thinking about the ramifications of their actions in disproportionate taxation at the top levels.... Edwards most likely left for that reason alone, so the Notley's and Trudeau's of the world also have to assume their share of moral responsibility on this
He is a well known philanthropist, gives generously (hugely) to charities, the arts and education (he put up enough cash to have a university business school in his name). In terms of the wealth he has amassed, he did so by creating companies, creating a great deal of employment, caused the investment of (literally) billions of $ in AB (and other parts of Canada), etc, etc, etc... The end result of this is that he made a ton of money for himself, but in doing so, a much larger multiple of what he made was dispersed throughout the community and population.
Given this factual description, think for one moment of the taxes that were generated from this.
Make no mistake, I am no cheer leader for Edwards, however, he's a great example because his path has been well documented.... Fact is, there are people like this in every city/town in every province throughout Canada representing every sector.
My message here is that continually leveraging this demographic will result in those people making similar decisions as Edwards and the biggest loser in the equation is Canada.