In the view we take of the case we do not deem it necessary to consider whether, with respect to the Federal question, there is any difference in the situation of the two defendants. It is assumed, in respect of each, that the jury were instructed that they might draw an unfavorable inference against him from his failure to testify, where it was within his power, in denial of the evidence which tended to incriminate him. The law of the state, as declared in the case at bar, which accords with other decisions (Parker v. State, 61 N. J. L. 308, 39 Atl. 651; State v. Wines, 65 N. J. L. 31, 46 Atl. 702; State v. Zdanowicz, 69 N. J. L. 619, 55 Atl. 743; State v. Banusik (N. J.) 64 Atl. 994), permitted such an inference to be drawn. The judicial act of the highest court of the state, in authoritatively construing and enforcing its laws, is the act of the state. Ex parte Virginia, 100 U.S. 339, 25 L. ed. 676; Scott v. McNeal, 154 U.S. 34, 38 L. ed. 896, 14 Sup. Ct. Rep. 1108; Chicago, B. & Q. R. Co. v. Chicago, 166 U.S. 226, 41 L. ed. 979, 17 Sup. Ct. Rep. 581. The general question, therefore, is, whether such a law violates the 14th Amendment, either by abridging the privileges or immunities of citizens of the United States, or by depriving persons of their life, liberty, or property without due process of law. In order to bring themselves within the protection of the Constitution it is incumbent on the defendants to prove two propositions: First, that the exemption from compulsory self-incrimination is guaranteed by the Federal Constitution against impairment by the states; and, second, if it be so guaranteed, that the exemption was in fact impaired in the case at bar. The first proposition naturally presents itself for earlier consideration. If the right here asserted is not a Federal right, that is the end of the case. We have no authority to go further and determine whether the state court has erred in the interpretation and enforcement of its own laws.