Does the federal estate tax need to be enforced by the states?

Nevertheless, so long as the states do not attempt by their laws or decisions to frustrate the policy of the federal government either in its determination of its taxes or in their collection, they are free to enforce legislative enactments designed[236 Cal.App.2d 664] to accomplish an equitable allocation of the actual burden or the ultimate impact of such taxes. As stated by the court in Riggs v. Del Drago, 317 U.S. 95, 98-99, 63 S.Ct. 109, 110-111, 87 L.Ed. 106, in reference to the federal estate tax: