They’ll still be known as the Duke and Duchess of Sussex, but said they won’t call their private charity the Sussex Royal Foundation. There is no legal jurisdiction by the Monarchy or other government officials over the use of the word ‘Royal’ overseas. However, The Duke and Duchess of Sussex are complying with Queen Elizabeth’s wishes that reduced the couple to private subjects of England.
Of course, the restrictions also don’t apply to Americans using the word royal. It may continue to be used when describing your in-laws, politicians and creditors as royal pains in the ass.