I don't know if you're a lawyer but I *certainly* am not.I base my previous comment on what I read once,which said that certain types agreements between states are specifically forbidden by the Constitution unless "approved" by Congress.What I read indicated that this agreement absolutely qualifies as being forbidden.
Of course I could have misunderstood what I read.It's just as possible that what I read was incorrect.
Assuming that *neither* of us are lawyers I wonder if one should be weighing in on this particular issue.
You are right...I am not a lawyer, but I have heard from conservative lawyers about state compacts for some time, and that they are a Constitutional permissible method.