It has been illegal for some time to shave or cut your horse's whiskers around the nose and eyes, but now the FEI has also announced that effective sanctions will be imposed on riders who do so from 1 July 2021.
No decision has yet been made regarding the national and regional competitions, but horses participating in international competitions whose whiskers has been clipped will be excluded. This also applies to participants in the Olympic Games.
Source: FEI