In sum, when the USSR became extinct, its bilateral, non-dispositive treaties lapsed.

CENTERFORSECURITYPOLICY: Center for Security Policy | Senate testimony of Douglas Feith and George Miron on ABM treaties and international law

In accordance with longstanding principles of international law, expounded with remarkable consistency by numerous officials and scholars from various countries over hundreds of years, when the USSR became extinct, its bilateral, non-dispositive treaties lapsed.

CENTERFORSECURITYPOLICY: Center For Security Policy

The only exception to what international lawyers call this "clean slate" rule is "dispositive" treaties--such as those that dispose of territory.

CENTERFORSECURITYPOLICY: What ABM Treaty?