Police have been barred from searching the Queen’s private estates for stolen or looted artefacts after ministers granted her a personal exemption from a law that protects the world’s cultural property, the Guardian can reveal. Buckingham Palace and the government are refusing to say why it was deemed necessary in 2017 to give the Queen an exemption that prevents police from searching Balmoral and Sandringham. A spokesperson for the Queen dismissed any suggestion that stolen or looted artefacts were being held on the monarch’s private estates. The Department for Digital, Culture, Media and Sport (DCMS), which gave the monarch the special dispensation, declined to say whether it had been proposed by royal aides or ministers. The DCMS is also keeping secret a set of emails that may shed light on why the Queen was granted immunity from the law. However, documents obtained under the Freedom of Information Act appear to suggest the department used opaque language in a parliamentary bill that obscured the purpose of the exemption from the public. The documents were requested by the Guardian as part of an ongoing investigation into Queen’s consent, an obscure parliamentary mechanism that gives the monarch advanced sight of proposed laws, including those affecting public functions, private property and personal interests. In February the Guardian published documents showing how the Queen had used the process to secretly lobby ministers to change draft legislation. In one instance, a bill was amended in order to conceal her “embarrassing” private wealth from the public, following an intervention from her private lawyer. More than 60,000 people have since signed a petition calling for an investigation into the Queen’s “worrying and undemocratic ability to influence the government behind closed doors”. The latest disclosure relates to the Cultural Property (Armed Conflicts) Act, a 2017 law that seeks to prevent the destruction of cultural heritage – such as monuments, archaeological sites, works of art and important books – in future wars. The decision to grant her an exemption from the law was privately spelled out in a letter in February 2016 to Buckingham Palace from a private secretary working for the then culture secretary, John Whittingdale. The letter follows the protocols of the arcane Queen’s consent mechanism, which requires ministers to request her permission to allow parliament to proceed with legislation that affects her. The private secretary explained that the bill contained “measures that established new powers of entry upon land and thereby affects the interests of the crown”. Although the law predominantly relates to the preservation and protection of cultural property in war zones, parts of it relate to stolen or looted artefacts that have been trafficked out of those countries. It made the buying or selling of these stolen or looted artefacts a criminal offence punishable by up to seven years in jail. Police have the power to search premises if it is suspected that they are being used to store illegally obtained artefacts. Whittingdale’s private secretary, who was not named, stated that the draft bill had been carefully phrased when it referred to the Queen’s special exemption. “Separately, we wish to ensure that the powers of part 4 of the bill are not exercisable in relation to Her Majesty’s private estates,” the official wrote. Part 4 of the bill gave the police powers to search properties where looted artefacts may be held and to seize them. The official continued: “In order to best deliver this outcome, we consider that the drafting at clause 35 strikes the optimum balance between clarity and propriety.” “While we could allude solely to Her Majesty’s private estates, the broader application to ‘in her private capacity’ ensures the totality of the bill does not apply and prevents any implication that some aspects of it might (which could occur if we referred solely to ‘private estates’),” the official wrote, adding: “We understand that the approach we have adopted is one which has precedent.” When it was passed in 2017, the bill contained the exemption in a clause that referred to “Her Majesty in her private capacity”. A DCMS spokesperson said: “It is incorrect to suggest that there was any direct attempt to obscure the purpose of any clause. It is common for legislation to include an exception for Her Majesty the Queen in her private capacity.” A palace spokesperson said: “The royal household can be consulted on bills in order to ensure the technical accuracy and consistency of the application of the bill to the crown, a complex legal principle governed by statute and common law. This process does not change the nature of any such bill.” The letter from Whittingdale’s private secretary makes clear that the exemption applies only to the Queen and her private estates. Police are still allowed to search properties within the crown estate, for example, a huge swathe of land that historically belonged to English monarchs and now belongs to the nation. A significant proportion of its profits are used to fund the monarchy. The Cultural Property Act is the result of an international push to clamp down on the destruction of cultural heritage during conflicts. In the wake of the destruction of artistic works at the hands of the Nazis during the second world war, the United Nations drew up an international treaty in 1954 to prevent the destruction of cultural heritage in future armed conflicts. It only became part of British law when the UK government passed the 2017 act.