At the very least, it would be considered legislation requiring a majority vote of both houses. However, it is now deemed to be valid and all congress can do is vote to disapprove, requiring a two-thirds vote to override the emperor's veto.
Pretty neat how that works, huh?
“Normally, this would be considered a treaty requiring two-thirds approval of the U.S. Senate.”
No, it Normally would not be, but ALWAYS.