The Prince is seeking a judicial review as the U.K. Home Office has restricted access to police protection while in Britain.
The Prince's lawyers argue that his own security can't adequately protect his family in the U.K. and Harry is offering to cover costs himself.
The Prince is being childishly demanding; he expects the same treatment after abandoning royal duties and risks being the first royal to launch a legal case against the Queen's government.
The level of risk to the Prince and his family remains the same despite his change in status. The security would come at no cost to the taxpayer - there is no reason not to allow Harry to pay.