ONLINE CASINO GAMBLING LAW FOR CANADIANS
When it comes to online gaming, Canadians tend to have it fairly good, unlike their neighbours to the south. Whereas it's illegal for Americans to gamble online and the U.S government has gone to great lengths to enforce this (this led to the notorious Black Friday a few years ago, where several online poker rooms where shut down by the U.S government), Canadians have no such ill fortune. While online gambling currently resides in a legal grey area, Canadians have no fear of being charged with any crime for gambling online. As such, they are welcomed at many online casinos, unlike Americans who are prevented from playing.
Of course, there are still legal aspects of online gambling to consider. Firstly, the online casino or gambling venture must effectrively be recognized as a legel entity. Otherwise you're considered to be dealing with a bookie, which is illegal in Canada, and a prosecutable offense. As most established online casinos operate legally within their jurisdictions and are fully licensed entities, there is minimal risk of such an occurence.
The other main consideration is related to taxes. Here again, Canadians have it quite good compared to their southern counterparts. Unlike a $50 million lottery win in the US, which would be heavily taxed, lottery winnings or winnings at any game of chance (effectively any form of gambling) are not taxable. The only small caveat is that if you derived a consistent source of income through gambling, with no other source of income to otherwise speak of over a lengthy series of time, the government may classify gambling to be your 'profession' or 'occupation', at which point your winnings would be considered taxable earnings. This scenario is highly unlikely to affect most people reading this, at least as it relates to online casinos. It's unlikely anyone will be quiting their day job to make their living playing online slots anytime soon.
Where the issue does become murkier is with professional poker players, some of whom can generate consistent earnings through playing poker (much more a game of skill, than pure luck). Such skilled players may reach a point where they would be forced to declare their poker winnings as their source of income and have it taxed.
So as long as your online casino of choice accepts Canadians and is a licensed gambling house, you have no worries when it comes to the legality of your gaming; and no fears over the taxman trying to take a slice of your winnings.