The proliferation of nuclear weapons is one of the most challenging security issues of today. In September 2009 reports of a newly discovered nuclear facility, the Fordow Fuel Enrichment Plant, raised the question if Iran is in compliance with the obligations under its Safeguards Agreement, which was concluded with the International Atomic Energy Agency in accordance with the Non-Proliferation Treaty. The paper seeks to provide a basis for understanding the problematic from an international legal perspective, using international treaty law as tool of analysis. For the interpretation of Iran''s rights and obligations the Vienna Convention on the Law of Treaties is applied on Iran''s Safeguards Agreement. Furthermore, the report discusses the overall legitimacy of the non-proliferation regime in general and the application of the non-proliferation rules in relation to Iran in particular. The analysis should be a useful key for accessing the complex system of international regulations, which make out the non-proliferation regime. Actors in the field, as well as anyone interested in better understanding the ongoing debate on a potential nuclear Iran, should find the report of value.