I saw one at a hotel entrance the other day that reads: ‘Smoking is not allowed in this building. If you observe someone smoking, complaints may be made to the management.’
So what’s wrong with that?
Well, what it actually says, is that if someone sees you watching someone smoking, they can make a complaint about you.
Warning. I’m going to talk about grammar now.
The problem is that it mixes passive and active tenses which changes the meaning.
It’s better to use the active tense throughout (and be more specific and simplify the language at the same time) i.e. ‘If you see someone smoking, please tell our staff at Reception.’
It doesn’t tell me where to complain about dodgy sign-writing.