The Duchy of Cornwall is a private estate that funds the public, charitable and private activities of the Prince of Wales, the Duchess of Cornwall, Prince William and Prince Harry.
Cornwall is as an administrative county of England, which is subject to UK legislation. The county elects MPs to the UK Parliament and has always been an integral part of the Union.
Similarly, the Isles of Scilly are represented in Parliament as part of the St. Ives constituency. The Government do not intend to change the legal position of the Duchy nor the constitutional position of Cornwall.