I would argue that proving somebody lied on an application would be easier than proving something like “this person is a danger to the US”. The 2nd is much subjective.
To prove that he lied on the application form, they would have to legally prove him as a terrorist. The legal process of proving someone is a terrorist would be same. So isn't it pointless?
I'm actually okay with that. Read it the other way around. You can only kick someone out for being dangerous if you can prove they are dangerous.