If you are asked by the organizers who you are, you should be open, honest, and clear about your intentions. This ethics rule about honestly representing who you are covers journalists and PR professionals.
Apparently, this rule was broken by a public affairs firm employee who misidentified herself to gain access to a labor group that opposes a proposed Walmart store planned in L.A.’s Chinatown. The firm fired her, and Walmart, in turn, fired the firm.
I’ve attended numerous events without a formal invitation, and I have never been kicked out even after I have identified myself and the organization I represented. Nearly all the time, they respect that someone from the “other side” is there to listen.
On most occasions, I’ve been pulled aside and asked to be respectful. I also was told that if I wanted to speak to reporters or participants, I should do so outside, so as not to disrupt the event. At one press conference, they gave me a seat up front even though I represented the other side.