What we have here is a difference in the spirit of the law and the word of the law.
He is doing the 'right' thing in the spirit of the law
but unfortunately the word of the law means his method is in question.
Tourists have the same legal protection as citizens, so legally it was the same as if he detained any of you by the threat of force. The only difference here is that they were illegal tourists, but unfortunately that difference currently has no legal difference. Yes they are trespassing on his property, but without him being a sworn LEO he can't legally do that much. If anyone trespassed on your property you can't detain them on it while calling the police about them being on it, nor can you detain someone on suspicion of breaking the law.
This guy is doing the right thing, and the law should be changed to suit.
All this is based upon my understanding and having once been near a holiday inn.