[mlo]

"To begin with, the answer is clear. If there was any constitutional issue resolved by the Civil War, it is that there is no right to secede."

Then why did the US specifically act to readmit the confederate states to the union? If they had no right to secede, then they never really left.

Also, if Virginia never left the union then the creation of the state of West Virginia, against the will of Virginia, would have been unconstitutional.

[Non-Sequitur]

Then why did the US specifically act to readmit the confederate states to the union?

The didn't. Once the rebellious states complied with the requirements placed on them by the Reconstruction Acts they had there delegations readmitted to Congress and not the states readmitted to the Union.

If they had no right to secede, then they never really left.

Bingo.

Also, if Virginia never left the union then the creation of the state of West Virginia, against the will of Virginia, would have been unconstitutional.

No. An organization of Virginia legislators who remained loyal to the U.S., and who coincidentally mainly came from western Virginia, got themselves recognized by Congress as the legitimate legislature. They voted to partition and Congress approved.