A contract to pay dollars, is according to the Supreme Court of the United States, a contract to pay lawful money of the United States. Lawful money of the United States is money declared to be legal tender in payment. Congress has declared United States coins and currency a legal tender. Therefore, United States coins and currency are lawful money.

The power of legal tender is not (expressly) given in the Constitution of the United States of America. In Juilliard v. Greenman (110 U.S. 421), the United States Supreme Court held that the power to declare its obligations a legal tender was an implied power that Congress had under the power to borrow money on the credit of the United States. This was based on the case of McCulloch v. Maryland. However, the case of McCulloch v. Maryland was wrongly decided. The concept of implied powers does not exist in the Constitution. Therefore, Congress does not have the power to declare anything a legal tender.

Thus, United States coins and currency are not lawful money. Or, in other words, the United States has no lawful money.

Which means that a contract to pay dollars, is a contract to pay dollars under the Constitution of the United States of America.

The question then is what is a dollar under the Constitution of the United States of America. The answer is a dollar under the Constitution is a Spanish Milled dollar coin, or its equivalent, in coin form, containing 371.25 grains of fine silver.