Export control by FSTEC
The S-400 system is manufactured by Almaz-Antey Air and Space Defense Corporation, Joint Stock Company. Almaz-Antey has two ways of selling products to foreign customers. The primary path is through the larger export control organization Rosoboronexport. Additionally they are licensed to sell arms “as an independent subject of military-technical cooperation…”2Almaz-Antey. 2018. “Almaz-Antey.” Almaz-Antey.Ru. The specific limitations of the license are unknown, so it isn’t clear exactly how Russian law would prevent a sale of an S-400 to a US company or government agent.
The legal body that governs Rosoboronexport and therefore Almaz-Antey is called “Federal Service for Technical and Export Control of Russia (FSTEC).” They list among their powers a number of specific provisions relating to export control, missile technologies, weapons and military equipment, state secrets, etc.3FSTEC. 2018. “Information on powers of FSTEC of Russia.” FSTEC.ru Any US agent working with local procurement would likely need a contacts at FSTEC, Rosoboronexport and Almaz-Antey.
Broadly speaking, the open-source picture of the Russian defense industrial base appears clearly organized, modern and efficient. It is a testament to Russia’s experience as a leading global arms purveyor that the process for buying weapons should be relatively transparent even to a layperson.
NATO would object
The US State Department voiced its “concern” about the Turkish purchase of the S400 in November of last year, specifically on the grounds that undermined NATO interoperability.4Nauert, Heather. 2017. “Department Press Briefing – September 12, 2017.” Department of State. Washington, DC. September 12 Turkish President Erdogan responded that Turkey has a right to purchase any self-defense equipment it needs, and that the US was applying a double-standard. Cyprus was required to hand over S-300 (precursor to the S-400 Triumf) to Greece, years earlier.5Majumdar, Dave. 2018. “The Real Reason NATO Should Fear Russia Selling S-400s to Turkey.” The National Interest. The US recognizes Turkey’s strategic value as a NATO member and has been measured in its expression of indignation. NATO Secretary General Jens Stoltenberg responded to a Turkish journalist who asked about the apparent double standard that what Turkey buys for self-defense is a “national decision.” He also noted that Turkey is in dialogue with the US to potentially buy Patriot missiles.6Stoltenberg, Jens. 2018. “Press Conference by NATO Secretary General Jens Stoltenberg Ahead of the Meetings of NATO Foreign Ministers.” NATO.int. Brussels Why Ankara would be interested in both systems is unclear.
One would expect that if the US were to reach out to Russia and begin negotiating the purchase of an S-400 system, other NATO member countries would find it confusing, especially if there was an expectation that the system was to be deployed alongside or in place of the popular Patriot system. Given the US core role in NATO, allies would have to seriously rethink their procurement models, force posture, and training models. The full ramifications of having an SA-21 Growler (NATO designation of the S-400) in service are beyond the scope of this memo. It is worth noting that NATO members may not be able to stop the US from signing a deal, but that deployment of one’s former/not-so-former adversary’s heavy weaponry would be unprecedented for the Cold War-era alliance. It is more plausible that the US would engage in procurement of adversary for use as an OPFOR training tool—something they did clandestinely during the Cold War.7 Weinberger, Sharon. 2010. “How Not to Buy a Russian Helicopter.” Foreign Policy, November 12
US sanctions may or may not be import barrier
Where there's a will, there's a waiver
US firms have been getting around federal sanctions on doing business with Russia since the interwar period. It is perhaps novel that the US Department of Defense would be forced to buy helicopters for Afghanis, thirty years after it was spending billions to train and arm Afghani mujahedeen to shoot them down. America’s relationship with Russia has never been completely opaque, logical or consistent and likely never will be. The sanctions regime that is in place currently is targeted at changing specific behavior, in specific regions of the world and in the emerging gray zone. The US and Russia do collaborate more or less successfully in other areas. Should there be an unexpected warrant for the United States to purchase an S-400 system, say for an ally or for red-teaming purposes, there is evidence to suggest that they will find a way to exempt a Russian defense agency in such a way as to purchase one without having to abandon the entire sanctions regime.