I believe in the Constitutional principle of the presumption of innocence. A Canadian should be allowed to leave Canada to travel wherever he wants. If he picks up arms against Canadian forces in a war zone, then we'll treat him like we do anyone else on the battlefield in conformity with the Geneva Convention. However, it is not up to us to find him guilty of treason just because he was somewhere and expect him to prove his innocence rather than require us to prove his guilt. The presumption of guilt is a dangerous slippery slope.
Let's take another parallel example. Up until recently it was illegal to be in a bawdy house. I am for making prostitution a fineable offence and in my opinion both parties in the transaction should be fined, and the fine should double for each repeat offence. That said, no one should be found guilty of prostitution for just being in a bawdy house. Maybe he's a plumber or electrician who got called in. Maybe he's the pizza delivery man who showed up just before the police raid. Maybe the residents hired her as their personal maid to clean, cook, and run errands. Maybe it's the prostitute's friend or family member visiting her for her birthday out of concern. There could be myriad valid reasons for being in a bawdy house. Making it an offence to just be in a bawdy house was struck down by the Supreme Court along with other prostitution-related laws and rightfully so.
If we want to make it easier to fine prostitutes and their clients, we could make the advertising of sexual services and adultery fineable offences but prohibit the police from spying to catch someone in the act and require at least two witnesses to or equivalent proof of the act. This would eliminate the need to prove a financial transaction while still protecting those having sex with their girlfriend in the privacy of their bedroom, affecting only those having sex in open public, and still protecting the presumption of innocence.
In the same way, we can make the promotion of terrorism, recruitment into a terrorist organization, training for the purpose of committing a terrorist attack, and many other such acts criminal offences. Never should a person be charged just for going or being somewhere given the myriad valid reasons for doing so. How would a person prove that he went to Iraq to see a friend? Why should he even need to prove it? Given the suffering ISIS has already caused him, why would the Government of Canada want to add to that suffering?
The day we abandon the principle of the presumption of innocence is the day fanatics win yet one more victory against us as we forego yet one more of our "Western values."