However, are there not USSC Rulings on treaties that say they can not over ride the U.S Constitution?
Yes, though as I noted earlier in the thread, currently there are 3 Supreme Court Justices who have indicated they would ignore the precedent of Heller and rule that there is no individual right to firearms at all. The fourth Justice likely leans that way. At least two of the Justices who voted for an individual right will be over 80 before 2016. I would like to see a couple of 6-3 or 7-2 pro-RKBA decisions from SCOTUS before I felt too comfortable relying on the Supreme Court to save us.
Luckily, there is zero chance this treaty gets ratified anytime soon. Even if you let the antis pick new Senators, it would still take them several elections to have the numbers necessary (assuming the Senators who signed the NRA letter remain true to their word - always a dangerous assumption when dealing with politicians).