"The Congress shall have power ... to provide for the punishment of counterfeiting the securities and current coin of the United States." This provision of the Constitution provides the Congress with the weapons to punish those who break the law by producing or issuing copies of legal money..
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The framers of constitution gave a great deal of weight to the creation of a national currency, one that did not yet exist. So much so that they provided a methodolgy right in the Congress ot make sure that the new currency would not be copied.