Standing for long periods at the mubaarak grave of Rasulullah (sallallahu alaihi wasallam)

In Madinah, when standing to give salam to the Nabi ﷺ at his blessed grave, the guards usually tell you to move away after a short while. Therefore you are not able to convey salams on behalf of all people who have asked you to do so. What some people do is that they despite being told off by the guards secretly stay longer until the guards physically push them away. Is it permissible to do so, given that you are certain that you do not cause harm and do not disrupt the flow of people by staying longer? Or is it necessary to immediately obey the command of the guards to move?