The six global powers working to reach a nuclear deal with Iran have agreed to reimpose any lifted sanction if Iran is caught deviating from the negotiated terms. This settlement helps the group move forward on concluding the deal by June 30.

Although the six UN powers (the United States, Britain, France, Germany, Russia and China) have agreed to this measure, Iran has not.

For some time now, the intricacies of sanction relief- including the timing of relief, the verification of compliance, and the method of restoration in the event that Iran reneged on the deal- have posed major obstacles for accord. The new understanding of ‘snap-back’ sanctions clears the path of the most difficult hurdles.

It has been decided that the International Atomic Energy Agency (IAEA) will regularly report on Iran’s nuclear activities. The Security Council will scrutinize these reports to ensure compliance. Any suspected deviation by Iran will be brought before a dispute resolution panel.

If it is found that Iran is not complying with the agreement, the sanctions will be restored.

“We pretty much have a solid agreement between the six on the snapback mechanism, Russians and Chinese included,” said a Western official. “But now the Iranians need to agree.”

Aside from Iran’s reluctance to commit to ‘snap-back’ sanctions, many questions about implementation loom. How would this mechanism function? How would it protect the US or Europe if Russia or China is capable of vetoing any move to restore sanctions?