BMW towing down through Italy, near Naples pulled into service area coffee stop. An Italian motorcyclist advised me he thought a trailer on a solo was illegal in Italy, but not really sure. As we were a few miles from home there was little I could do about it, so carried on. Three days later pulled into another service area /coffee shop. Three police cars with drivers taking their coffee there . A fourth cop car pulled in behind me, the officer got out, without saying a word, walked round my BM and trailer, looked hard at it, walked round again, stood and pondered, shrugged his shoulders and went to join his mates.
I could virtually see the speech bubble over his head " I think that trailer is illegal, but I can't face the paper work just now, let me at the coffee"
No problems subsequently in France ,Italy. Greece, Switzerland (although the police made me buy a Ticket for the trailer as well as the bike) or Luxembourg. We were in no hurry so probably cruising at 50/60 ish mph. One of our all time great trips for a month. 47Deg C in Greek Meteora and minus 3deg C crossing the Alps. Only trouble was "pinking" in excessive heat. Befriended by a very attractive Senorita who insisted on pictures with us