fraud upon a statute

It is not a case of a direct reservation of a higher interest than the law allows, since on the face of the note, only six per cent. is reserved; but the facts are calculated to present one of those cases in which a device is resorted to, by which is reserved a higher profit than the legal interest, under a mask thrown over the transaction; to wit, by taking a note payable in gold or silver, for a loan of depreciated paper... That the law will not tolerate such transactions has long been settled, for a fraud upon a statute is a violation of the statute.