They called it the Lisbon Protocol.
In 1991, the U.S. and Russia agreed to historic reductions in nuclear weapons. But there was a hitch: Russia didn't exactly own all of its nukes. When the Soviet Union collapsed, lots of them were left in the former vassal states of Belarus, Ukraine and Kazakhstan. Under the protocol, all the nukes from these countries would be transferred to Russian control or destroyed.
Ukraine promptly negotiated a pact to make this happen. Moscow and the West pledged to respect and preserve Ukrainian sovereignty and borders. In return, Kiev handed over its nuclear arms.
Last week, it became abundantly clear that the deal was off -- at least as far as Moscow was concerned. Russian tanks rolled into Crimea.