One of the main problems is that the security people never identified themselves to Hoflinger, apparently. In order to enforce any sort of order to leave property, you need to actually be an authority, and cite yourself as such.

All this is coming from my time as a bouncer and a doorman, by the way. If the person you’re asking to leave is not drunk, when you’re a bouncer, and not violent, there is very, very, very little you’re allowed to do to get them to leave. You really do just have to call the cops on them. You certainly can’t cuff them to a chair. If they get at all physical with you, you can respond with equal or lesser force; you are not allowed to escalate unless they have committed a felony crime.

Now, if that’s true for a clearly-identified bouncer, an employee of an actual business, at a very obviously private bar, I really doubt that it’s legal for a security guard who failed to identify himself has the right to detain a reporter at a public event.