Customary international law is unstable and has been slowly eroding navigational rights -- ratifying UNCLOS will provide stability

The Convention reduces, but doesn’t wholly eliminate, the indeterminacy inherent in customary law.  The Convention also provides greater stability and predictability. Here it should be noted that the LOS Convention’s articles can only be amended through an elaborate process that, by design, provides the kind of stability the U.S. has long sought in the maritime domain.  By contrast, customary law rules evolve by the practice of nations asserting, acceding to or persistently objecting to new norms, thus introducing unwelcome uncertainty into the nation’s maritime affairs. Moreover, as Edwin Williamson, President George H.W. Bush’s State Department Legal Advisor noted, the history of customary international law “reflects a steady deterioration of the freedom of the seas to the detriment of the essential rights of maritime nations, such as the U.S.”