Justice Thomas's point in that dissention is a good one.  If the Supreme Court has original jurisdiction for a dispute between two states, how can they decline the case?  How else does the dispute get resolved?  When the SC decline the Texas case for lack of standing, I assume they mean Texas has a lack of standing over that specific issue, not overall.  It still seems like a weak reason, maybe the conservatives on the court feel another case would be the better way to go?