The Duke of Sussex began a legal battle against the Home Office in February after it refused to allow him to pay for his own protection while visiting the UK.
The ruling in his favour on Friday, July 22, at the High Court means he will now be able to take the case for a judicial review, Dailystar reports.
He and his team had argued that his US-based entourage do not have sufficient jurisdiction in Britain to be able to protect him properly.
They further argued his hiring of police officers during the duration of his trips would come at no cost to the taxpayer.
But the Executive Committee for the Protection of Royalty and Public Figures (Ravec), which falls under the remit of the Home Office, ruled last June that he could no longer be entitled to the “same degree” of security as he is now a private citizen.
Harry’s lawyers said in an appeal last month that the decision had been made with “procedural unfairness” as he had not been able to make “informed representations” before his application was denied.
In the first stage of the case earlier this month, the duke’s lawyers asked Mr Justice Swift to grant permission for a full hearing to have a judge review the Home Office’s decision.
In a judgment on Friday, the High Court judge said the case could proceed, granting permission for part of Harry’s claim to have a judicial review.
Mr Justice Swift said: “The application for permission to apply for judicial review is allowed in part and refused in part.”
A written argument from Shaeed Fatima QC had earlier stated that the decision had been “materially prejudiced” because “among other things, his offer to pay (for security) was not conveyed to Ravec before the decision was made”.
However, lawyers for the Home Office say Ravec was entitled to reach the decision it did, which is that Harry’s security arrangements will be considered on a “case by case” basis, and argue that permission for a full judicial review should be refused.
Sir James Eadie QC, representing the Home Office, said in written arguments that any tensions between Harry and Royal Household officials are “irrelevant” to his change in status.