Negative play? As opposed to players off their feet/sealing off and whatever else that effectively prevents defenders from any meaningful contest for possession post breaksown?
The tactic above is totally within the laws of the game. Whereas I don't care what weasel words are used to justify players putting their hands on the ground beyond the ball, with shoulders lower than hips, players flopping all over the ball etc etc etc - that isn't within the laws as writ.
If "we" don't like what "we" see then i suggest the better method is to create a situation whereby rucks are genuine contests again, ratjher than legislate against a tactic that is a reaction to the fact that rmost "rucks" cannot be contested in any meaningful manner.
Keep players on their feet and we are a long way towards that goal.
First principle of play anyone?
didds