The internet has helped to open up the world of casino gambling. Canadians not only have easier access to casinos than ever before, but also face the choice of whether to gamble at a domestic casino, or offshore. Are there any legal problems with gambling in an overseas casino? In a word: no.
Gambling in Canada is perfectly legal (assuming the establishment in question has the right license), so offshore gambling is entirely optional. That said, Canadian casinos must have the appropriate permit (usually acquired from the government authorities, or the Kahnawake Gaming Commission). Without the right license, onshore casinos cannot operate legally.
A nice aspect of Canadian casinos is that they're tailored to the nation's market. This means if you fancy trying your hand at sports betting, popular Canadian sports are likely to be covered better than a casino based in the United Kingdom, for example. On the patriotic side, homegrown casinos also pay tax in Canada, and are governed by the nation's laws, so you can be relatively confident of legal/financial redress if anything goes wrong.
On the flipside, if you're betting on a Canadian casino it can be as well to check it does have the right license for your territory. Because if it doesn't appear to have one, it may be operating illegally, and be best avoided.
Another downside to betting domestically can be restrictions on payment/deposit options. For example, Mastercard is often permitted as a deposit option but not for withdrawals. Similarly, the e-wallet Skrill used to be very popular as a payment option but is currently not accepted in Canadian casinos.
Whilst there are plenty of Canadian casinos, there are even more offshore betting establishments. And the more casinos, the more special offers, welcome bonuses, and other promotions to choose from. On top of this, there's a broader selection of games. On the security/trustworthiness front, major casinos all around the world have a reputation to protect. Because of this they tend to have robust security and comply with the legal requirements of their particular territory (often Malta, the United Kingdom, or Gibraltar).
In addition to extra gaming opportunities, foreign casinos can also have more developed sports betting markets.
The nature of Canada's gambling laws also means that overseas casinos are usually perfectly happy for Canadians to gamble there. Nor should it be a problem gambling in Canadian dollars. Only a tiny number of foreign casinos have been subjected to legal action by Canada, and no gambler from the country has been affected in this way.
In short, it's fine to gamble in offshore casinos. Not only is it perfectly legal, you may well enjoy a better range of games and a slightly broader selection of payment options.