The compacts clause and the "full faith and credit" clause were meant to control how states interact with each other, with Congressional oversight.
That's not what Illinois is doing to Texas. Illinois is supporting a dissident minority faction to obstruct the lawful government of another state.
-PJ
“It’s a federal matter because one state (Illinois) is interfering with the legitimate operations of another state (Texas) with the consent and active involvement of its Governor (Pritzker).”
Interference in anther state’s “legitimate operations” is a pretty loosey-goosy claim. If the Texas legislature thinks that the Democrats’ flight is a crime, let them make that claim in a Texas court.