AG permissions

Earlier today i was asked to help clear some RM blocks that were placed in someones town by anther member (griefing) and i was unable to clear them because i could not edit another towns area. also another town had a water pump that was going straigt into the sea and making the area look terrible and again i could not stop it because it was in someones town. Surely as an anti grief i should be able to build anywhere if needed so that i can help with these situations?
Thanks

I will come help if needed

i got the owner of that town to trust me so i could do it but if that person isnt online i dont want to have to call someone in everytime for a simple problem as delete a rm block or a sign etc