Sovereign coinage

there is attached to such ownership those limitations which public policy may require by reason of their quality as a legal tender and as a medium of exchange. These limitations are due to the fact that public law gives to such coinage a value which does not attach as a mere consequence of intrinsic value. Their quality as a legal tender is an attribute of law aside from their bullion value. They bear, therefore, the impress of sovereign power which fixes value and authorizes their use in exchange.