We are an informal group that fly together and as long as you are flying a model airplane every one is welcome to fly. Not many rules except that one is courteous to others and follow basic safety. Once a new guy landed at the field with his mega hi technology multirotor. This was not a hobby grade machine but a commercial grade with big 18-20 inch multi props. He was welcome to fly and he was stationed at one end of the flight line, while I was towards the other end .
While I was up in the air, the multi copter whirred overhead from my rear, and crossed the flight line. I ignored it once, then it happened again when he came flying along the flight line and pretty close to people. Over the sound of engines and motors I had to hail a caution to the flyer to desist as it was distracting while I was in the air. Then it happens third time and and I yelled and cussed at him. After I landed I went to talk to him, and he took issues with this. I was lucky that almost every one else realized what was happening and tried to make the fellow understand, there was a heated argument. However he never showed up again.
I guess once in a while there will be people who will need to be cautioned and made to follow basic safety rules