One of the key principles of international law is the concept of reciprocity. Very simply, it means countries allow other countries to do things because they are extended the same privileges.

The classic example of reciprocity in action is diplomatic immunity: Countries do not like hosting foreign nationals that are immune from prosecution, they allow it because their own sovereign representatives enjoy those very same privileges when they are overseas.

On 28 September US lawmakers incurred the potential wrath of reciprocity when they rejected President Barack Obama’s veto of the Justice Against Sponsors of Terrorism Act (JASTA), which allows relatives of the victims of the 11 September 2001 attacks in New York to sue the government of Saudi Arabia.

A day later the Saudi foreign ministry reacted by saying the decision made on Capitol Hill will weaken sovereign immunity, echoing comments on reciprocal actions made by President Obama when he outlined his reasons for vetoing the bill.

There could be significant ramifications for business in Saudi Arabia. There have already been reports that the pending court proceedings could hamper the kingdom’s plans to sell $10bn of bonds as some international investors may not want to buy Saudi securities. Any delay would prevent much needed cash being pumped into the Saudi economy and stifle economic activity.

As the relationship between Washington and Riyadh becomes more tense, reciprocal actions could start to affect US firms looking to win work. Experience from the past has shown that countries can be shunned when it comes to awarding government contracts when international relations are put under strain, and there is a possibilty that this could now happen with US firms.

Some US companies have already spoken out against the bill, but that may not be enough to prevent them from being dragged into a problem that many on both sides would prefer to avoid.