Congress may prescribe the law to prove or authenticate a legislative Act or judicial Act of a State. This means that Congress sets the process by which state authorities prove a submission to be an authentic copy of a State Act. Congress did set the process. At the time of the WBTS, it had been set by the Act of May 26, 1790. Currently it is set by 28 USC 1738.
This is the official opinion of the Unites States Legislative branch by way of its Act of May 26, 1790, and of the United States Executive branch by way of signing the legislation, and of the United States Judicial branch by way of the U.S. Supreme Court decision in MILWAUKEE COUNTY v. M.E. WHITE CO., 296 U.S. 268 (1935).
The process was never set for secession. The states should've gave the Congress the opportunity to set the laws for secession to be proven and when they didn't, they were in rebellion.
This is the official opinion of the Unites States Legislative branch by way of its Act of May 26, 1790, and of the United States Executive branch by way of signing the legislation, and of the United States Judicial branch by way of the U.S. Supreme Court decision in MILWAUKEE COUNTY v. M.E. WHITE CO., 296 U.S. 268 (1935).
Article IV says the Congress can prescribe laws as to the effect of acts. Obviously that had not been done yet for secession. The seceding states should've followed Article IV.