Well, then it looks like they’re being easy on him and his case is probably not so aggravated that it warrants immediate detention and deportation. He’s just being told his visa has been canceled and he is to leave in 2 weeks. So they are within their rights to cancel a visa if a condition is met but to be immediately detained it steps it up a notch, and future admission may be difficult if not impossible.
And you don’t even have to commit crimes to be asked to leave in 2 weeks… violating terms of the ARC does that too.
Perhaps we can ask for anyone who’s well versed in Taiwanese immigration laws to chime in (I am not, I only know in the US it’s 2 different thing. “Deportation” is not even in their legal language anymore, it’s called “removal”. “Voluntary Departure” is actually a legal procedure there where you’re given a time to leave the country and it doesn’t count as “removal”)