Civilian use is permitted on land, but use of the unmodified flag at sea is restricted to military vessels. Unauthorised use of the flag in the 17th century to avoid paying harbour duties – a privilege restricted to naval ships – caused James's successor, Charles I, to order that use of the flag on naval vessels be restricted to His Majesty's ships "upon pain of Our high displeasure." It remains a criminal offence under the Merchant Shipping Act 1995 to display the Union Flag (other than the "pilot jack" – see below) from a British ship. Naval ships will fly the white ensign, merchant and private boats can fly the red ensign, others with special permission such as naval yacht clubs can fly the blue ensign. All of the coloured ensigns contain the union flag as part of the design.