Obama cannot sign a treaty to take away the 2nd Ammendment. The Constiution is Supreme. The SC has backed that up many times.
Reid v. Covert
P.17 - There is nothing new or unique about what we say here. This Court has regularly and uniformly recognized the supremacy of the Constitution over a treaty.*fn33 For example, in Geofroy v. Riggs, 133 U.S. 258, 267, it declared:
P.18 - This Court has also repeatedly taken the position that an Act of Congress, which must comply with the Constitution, is on a full parity with a treaty, and that when a statute which is subsequent in time is inconsistent with a treaty, the statute to the extent of conflict renders the treaty null.*fn34 It would be completely anomalous to say that a treaty need not comply with the Constitution when such an agreement can be overridden by a statute that must conform to that instrument.
Our FRiend, Mechanicos, posted the relevant case histories to clear up my mind on this point.
Better look at the Supremacy Clause again, particularly its punctuation. There is a reason Patrick Henry objected to it in the Virginia Ratifying Convention.
Further, I can show you a treaty whose terms so WILDLY exceed the enumerated powers set forth by Congress as to be unarguably unconstitutional that has stood at the core of environmental law for forty years with hundreds if not thousands of cases pursuant to that understanding. So to argue that Reid v. Covert is the core standard of jurisprudence is just silly. You and I may wish to read the Constitution that way, but I'm afraid Mr. Henry may have been right.