In May 2019, World Rugby published guidelines for dealing with high tackles and shoulder charges. The framework document lives here or in the pdf attached. WR says:
Under Law 9.11, the referee is always entitled to issue a red or yellow card for anything that they deem to be reckless or dangerous.
However, the following guideline is intended to improve consistency in application of sanctions by distinguishing between dangerous tackles that warrant a penalty, yellow card or red card. The framework also supports protection of the head of both players by consistently and frequently sanctioning the tackle behaviour that is known to be the highest risk.