Ordinarily your statement would be correct. The Supremacy Clause and Article I would govern, and States would be forbidden to lay taxes or claims on federal property.
However, we are talking about secession, in which case the Constitution and the Union lapse, the States cease to be parts of the Union bound by the Supremacy Clause, and their officers and citizens cease to be citizens of the United States, or to have any political intercourse with the remaining States.
That is what secession really means.
So you are no longer claiming secession is legal under U.S. law.
In any case, the United States Supreme Court ruled all acts and ordinances of secession null and void in law. So it is moot any way.
Walt
In the case of the United States during the ACW era, secession meant treason and unwarranted revolution.
Walt
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