Complex sentence: As a chemical weapon, it is classified as a weapon of mass destruction by the United Nations, according to UN Resolution 687, and its production and stockpiling was outlawed by the Chemical Weapons Convention of 1993.
Split into simpler sentences: As a chemical weapon, it is classified as a weapon of mass destruction by the United Nations. Pursuant to UN Resolution 687 its production and stockpiling was outlawed globally by the Chemical Weapons Convention of 1993.