Third, because of the legal restrictions that these UN resolutions impose on all states, including on Western states that are in the process of negotiating with Iran, P5+1 negotiators cannot legally offer Iran any technical incentive to secure its cooperation. The Security Council effectively bans most forms of assistance to, and investment in, Iran’s nuclear and energy sector. That restricts the P5+1 negotiators, which are legally bound to maintain the full force of the resolutions, from offering any captivating alternative to Iran.
To illustrate the point, Germany’s Green Party submitted a proposal last year in which the German government would help Iran build a solar energy facility in exchange for Iran curbing some aspects of its nuclear program. Such a proposition, and similar ones, could have been put on the table by the P5+1 to increase the negotiations change of success. But the Security Council renders such creative initiatives irrelevant as their realization would be illegal under its resolutions.
In other words, because of these legal strictures, the P5+1 goes to the negotiation table without having the capacity to offer its counterpart any positive incentive, something that most negotiators would find a handicap rather than a leverage to their advantage.
Of course, despite these legal restrictions, various international actors have occasionally been able to offer promising deals to Iran. For example, in May 2010, Brazil and Turkey persuaded Tehran to ship 1200 kg (2640 pounds) of its low-enriched uranium to Turkey (as a confidence-building measure) based on a proposal that was initially drafted by the Obama administration. However, the United States itself subsequently blocked the bargain on the ground that it still did not meet the restrictive demands of the Security Council.