120. The States comprising the Union possess equal powers and are subject to the same limitations. This means, in brief, that they have, respectively, the same jurisdiction. The sovereignty of one State is equal to the sovereignty of another. Because of this equality, they are all subject to the same rules of State comity. The aspects of this mutual equality are numerous and are the subject of provisions of the Constitution.[304] In so far as a State possesses jurisdiction it may exercise authority.[305] This rule is fundamental in American constitutional law. The Constitution of the United States confers no new power of jurisdiction by simply regulating the effect of the acknowledged jurisdiction over persons and things within a State.[306] Thus a State cannot make its law valid in another State; the validity of a State law depends upon the will of the State in which the validity is claimed. From this it follows that “the jurisdiction of any (State) court exercising authority over a subject (_i. e._, persons or property) may be inquired into in every other (State) court when the proceedings in the former are relied upon and brought before the latter by a party claiming the benefit of such proceedings.”[307] So, despite the fourth article of the Constitution as to “full faith and credit,” and “public acts, records, and judicial proceedings” in the several States, “a judgment rendered in any State may be questioned in a collateral proceeding in another State.”[308] 121. This principle is disclosed by examination of the States as civil and political entities, for: It is equally well settled that the several States of the Union are to be considered in this respect as foreign to each other, and that the courts of one State are not presumed to know, and therefore, not bound to take judicial notice of the laws of another State.[309] Therefore, whenever it becomes necessary for a court of one State, in order to give full faith and credit to a judgment rendered in another State, to ascertain the effect which it has in that State, the law of that State must be proved, like any other fact.[310]