The crown has long been used as a symbol of royal power and authority. Like the sceptre, the crown is a visible badge of office, granting the wearer, it's possessor, the absolute right to rule. That authority to rule was often held to be divinely inspired. In the Christian tradition the garland of thorns placed on Christ's head during the ordeal of his crucifixion is know as the "Crown of Thorns". The centerpiece of any coronation of a new monarch is always the moment when the new King, Queen, or Emperor has the state crown placed upon their head. At that moment the power to rule is transferred to the new monarch.
Many groups have used the crown to symbolize the power and authority to lead or command. When it is combined with a cross, one of the meanings of the crown is "victory," and the cross symbolizes Christianity. Many Royal crowns in Europe incorporated the Christian Cross into their design, reinforcing the Monarch's claim that their right to the throne was a divine right and that the Monarch was guided by the hand of God.
As a tattoo symbol, the crown doesn't just mean the right of one person to command another. It symbolizes and individual's sovereignty over their own life, feelings, thoughts, and actions. The crown symbolizes self-control, and is a reminder to use power and authority wisely and justly.