We allow citizen to retain their American(or whatever their current citizenship).
The legal definition of treason in the US Constitution is:
Section 3 - Treason
Treason against the United States, shall consist only in levying War against them, or in adhering to their Enemies, giving them Aid and Comfort. No Person shall be convicted of Treason unless on the Testimony of two Witnesses to the same overt Act, or on Confession in open Court.
The Nation of Deseret is not an enemy to the United States. It is our goal to maintain peaceful and friendly relations with the United States of America.
Now if we told everyone to hoard their guns and ammo and move to a small compound in the Maontains, then you should probably worry.