TEHRAN - On 8 May 2018, as confirmed by the revised Frequently Asked Questions (the "FAQ") from the U.S. Treasury's Office of Foreign Assets Control (“OFAC”), the American President issued a National Security Presidential Memorandum (“NSPM”) directing the Secretary of State and the Secretary of the Treasury to prepare immediately for the reimposition of all of the U.S. sanctions lifted or waived in connection with the Joint Comprehensive Plan of Action (“JCPOA" or “Nuclear Deal”).

The FAQ makes clear that the NSPM presages the reimposition of all sanctions, include both primary and secondary sanctions, both nuclear and non-nuclear.                                  
According to FAQ, the snapback will occur in three phases detailed here below:

8 May 2018: Beginning of the Wind-Down Period
Starting 8 May, many forms of new business with Iran or Iranian entities become henceforth prohibited, and entities already engaged in business with Iran are instructed by OFAC to commence the wind-down of their activities. This wind-down will operate through two overlapping periods of 90 and 180 days respectively, subject to the nature of such business.

5 August 2018: Expiration of the 90 day wind-down period and beginning of sanctioning associated activities

The 90-day wind-down period for the following named activities is set to expire on 5 August 2018, the day after which nearly all activity associated therewith may be sanctionable, including:
-    Transactions in Iranian rials, in particular “significant transactions related to the purchase or sale of Iranian rials, or the maintenance of significant funds or accounts outside the territory of Iran denominated in the Iranian rials";
-    Trade in gold/precious metals, graphite, and raw, or semi-finished metals;
-    The Iranian "automotive sector", ostensibly in its entirety.
4 November 2018: Expiration of the 180 day wind-down period and beginning of sanctioning associated activities

The 180-day wind-down period for the following named activities is set to expire on 4 November 2018; the day after which nearly all activity associated therewith may be sanctionable, including:
-    Petroleum-related transactions with, among others, the National Iranian Oil Company (NIOC), Naftiran Intertrade Company (NICO), and National Iranian Tanker Company (NITC), including the purchase of petroleum, petroleum products, or petrochemical products from Iran;
-    Associated services related to these petroleum-related activities, which should be understood as meaning services – including technical assistance, training, insurance, re-insurance, brokering, transportation, or financial service – necessary and ordinarily incident to the underlying activity (such definition promulgated as per OFAC FAQ dated 16 January, 2016) ;
-    Engagement of foreign financial institutions with the Central Bank of Iran and/or with certain designated Iranian financial institutions;
-    Provision of specialized financial messaging services to the Central Bank of Iran and certain Iranian financial institutions (as per Section 104(c)(2)(E)(ii) of 2010 CISADA). Pursuant to this provision, transactions between Iranian and foreign financial institutions relying on the “SWIFT” system which allows transfer of money across international borders, may be once again blocked;
-    Insurance industry/underwriting activities;
-    Iran's energy sector more broadly.
In addition, more than 400 persons and entities removed from the OFAC SDN List under the JCPOA will be per section 1.3 of FAQ, once again thusly designated no later than 5 November 2018, effectively exposing any persons dealing with them thereafter to secondary sanctions.  
The FAQ also indicates that OFAC will revoke JCPOA-related authorizations for certain limited activities of U.S. persons vis-à-vis Iran, including carpets and foodstuffs; moreover, the specific licenses for the sales of commercial passenger aircraft, parts and services and any contingent contracts previously authorized under the General License I will be revoked and, OFAC has said it will no longer consider new or pending specific licenses for aircraft sales.
Moreover, as would be expected, General License H, which previously authorized foreign subsidiaries of U.S. enterprises to engage in certain kinds of Iranian business, is to be modified/revoked, accordingly.
-----Guidance on grandfathering  
The 8 May FAQ also elaborated upon the nature of so-called grandfathering of payments which are contractually specified under activities previously permitted by the JCPOA, resolving the long-standing question of legality of payments made under contracts initiated prior to snapback.
OFAC has stated that they will allow for non-U.S., non-Iranian persons which are owed payment for goods and services under a contract entered into before 8 May 2018, to be permitted to receive payment after the end of the wind-down period/the start of the reimposition of sanctions, under the terms of such contracts. Such payment authorization is made on the condition that the goods or services are fully provided prior to 5 August 2018 or 4 November 2018, as applicable, and that the payment does not involve U.S. persons or the U.S. financial system (which, in any case, is not permitted even prior to any snapback). This is also true for loans or credits.
What now?  
While it is difficult to find aspects of the FAQ which leave substantial room for a continuation of commerce between nations subject to/choosing to obey U.S. secondary sanctions, there are certain finer points of the language which are to be noted:

1)    The FAQ explains that sanctions will be reimposed on petroleum-related transactions and purchases of petroleum, petroleum products and petrochemical products. The FAQ does not, however, mention gas, in any context, although the FAQ does state that the Energy Sector will once again be subject to sanctions.  It is not clear whether the exclusion of the mention of "gas" provides a window for certain kinds of transactions, but by the same token, it is difficult to envision, at least immediately, how the reimposition of energy sector-wide sanctions would not, perforce, include gas.

2)    The FAQ furthermore does not make mention of the dispute mechanisms embedded in the JCPOA itself.  Pursuant to the complaint facilities contained therein, Iran may now, if it chooses to do so, file an action against the U.S. within the UN whereby the UN Security Council may undertake a resolution not to reimpose sanctions on Iran; however, the issue here is two-fold in that, even if such a resolution could be passed, the UN cannot necessarily force the U.S. not to reimpose unilateral sanctions (primary and secondary) on Iran, and moreover, with U.S.’s United Nations Security Council veto power, it would seem virtually impossible for any such resolution of any kind which could limit the effects of snapback on Iran to be passed.

3)    The FAQ does not expressly exclude transactions in non-USD, non-rial currencies, and so although SWIFT may be at risk of closure vis-à-vis Iran, other financial transfer systems, including TARGET2, and bilateral payments frameworks such as those existing between Iran and Turkey, Russia and China, may offer viable alternatives over time.

In conclusion, preservation of the JCPOA or its enabling conditions for commerce between the globe and Iran will require swift and decisive action by the European Union, which has indicated an intent to protect the interests of its companies which have invested billions in Iran post-JCPOA.  Such action could include the enactment of blocking regulations, the passing of council resolution(s) offsetting the ramifications of the NSPM-imposed snapback, or otherwise the filing of a WTO-based complaint against the U.S. to attempt to reverse the sanctions reimposition.

Absent these kinds of measures, it would seem that there is a likelihood that many companies engaged in Iranian business must contemplate the implications of the snapback for their business, and how they can wind down or otherwise transfer their existing project interests to parties which do not perceive the threat of sanctions consequences for remaining in Iran.