Sure. But Article IV does not prohibit secession. But secession is not a legislative act - it is the act of the people of a sovereign state in convention.
It sets the rules for states to prove their acts, secession being an act of a state, it therefore falls under Article IV.
But secession is not a legislative act - it is the act of the people of a sovereign state in convention.
A public act, yes, as Article IV says.