A key provision in the bipartisan Iran sanctions bill that the Senate introduced last week is causing widespread confusion and debate about its potential impact.

Advocates of the Iran nuclear deal argue that the bill from Senate Foreign Relations Chairman Bob Corker, R-Tenn., would label the 100,000-strong Islamic Revolutionary Guard Corps (IRGC) a terrorist group and trigger a showdown between the United States and Iran. Others, however, say it wouldn't add any new sanctions on Iran.

In a testament to the complexities of US sanctions law, both sides could be right. In fact, what people think the law does — not its actual substance — may well decide both its fate in Congress and the reaction in Iran.

At issue is a provision in Corker's bill that calls for extending terrorism sanctions to the IRGC. Those sanctions are codified under an executive order signed by President George W. Bush in October 2001 that blocks the property of designated terrorists and prohibits transactions with them; Bush expanded the order to cover the IRGC's Quds Force in 2007, and Corker's bill would treat the entire IRGC the same way.