In my town the we have a shopping mall that has a ban on people under 18 being in the mall on weekends without an adult due to gang problems.The security guards there routinely make citizen arrests on people that have been escorted out once and then have returned. So just something to think about if the security guard decides to make a citizen arrest on you for trespassing after youve been warned and you dont "think" he has the right to, you could find yourself in a great deal of legal trouble especially if you resist or do get away and he/she gets hurt. Somtimes its not worth making a point that only you will appreciate anyway.