It was an advantage to the negotiators of the CTBT that a number of disarmament treaties already existed that included on-site inspection mechanisms.  Still, the negotiations proved challenging. Negotiators had to strike a fine balance between the expected benefits and the political risks.

A key benefit of an on-site inspection regime is that it deters potential violators from conducting nuclear explosions in the first place.  It thus increases confidence in States’ compliance with the Treaty.  Provisions for on-site inspections strengthen the notion of a verifiable Treaty and thus help garner support for it.

On the risk side of the balance sheet is the false sense of security on-site inspections could create. An inspection may fail to prove an actual violation which may have ensuing political implications, and an inspection may not be carried out due to implied costs and complexity. During the CTBT negotiations, the risk-benefit discussion concentrated on how to ensure a State Party’s right to protect its national security versus conducting an effective and thorough on-site inspection.

On-site inspection in the Treaty
The Treaty stipulates that on-site inspections can only be invoked once the Treaty has entered into force.  The Treaty prescribes how an inspection is triggered; how it is prepared and conducted; what techniques and procedures can be applied; which information an inspection report should contain; and what possible steps could follow the report’s examination by the organization’s main executive organ, the Executive Council. The Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) is now working to build up the OSI regime, so that the OSI capability will be available following the Treaty’s entry into force.