A situation arose in an u13 game I was reffing when a defender went to tackle the attacking player who had the ball but as they made contact the ball carrier put the ball under one arm and 'tackled the tackler' by lifting his leg causing him to go to ground. I played on at the time but on reflection I wonder if this constituted tackling a player without the ball?
As you will be aware, at that level the referee is also part coach. What you describe is not something we want to be encouraging (you are correct in that technically he is playing a man without the ball), so needs to be dealt with at the time. By allowing the game to play on you are missing the opportunity to educate the player, so he may think this is acceptable practise.
The Rugby Refs advice would be to stop the game and award a penalty for playing the man without the ball, but don't restart without first having a word with the player to explain what he has done wrong. The ball carrier may fend off the other player (nb: not at all age groups), but may not attempt to tackle him.
This is not something The Rugby Ref has come across before Mike, so thanks for highlighting it.
The Rugby Ref