In recent weeks, the UN, the US, the EU and others partners have announced new sanctions to hold Iran accountable for conduct surrounding its nuclear and ballistic missile programmes. These actions have significantly expanded and deepened existing sanctions, and seek to combat Iranian efforts to evade increasingly stringent global restrictions.

Substantial attention has already been paid to sanctions in Iran's banking and energy sectors. But the latest round of measures also sharpens the focus on another sector that is a critical lifeline for Iran's proliferation and evasion: shipping. Some of Iran's most dangerous cargo continues to come and go from Iran's ports, so we must redouble our vigilance over both their domestic shipping lines, and attempts to use third-country shippers and freight forwarders for illicit cargo.

Iran has consistently used its national maritime carrier, the Islamic Republic of Iran Shipping Lines (IRISL), to advance its missile programmes and to carry other military cargoes. Some shipments have been stopped, and were clear violations of Security Council resolutions – including arms shipments believed to have been destined for Syria, for transfer to Hizbollah. Using an authority designed to freeze the assets of proliferators of weapons of mass destruction, the US Treasury's Office of Foreign Assets Control (OFAC) first brought sanctions against IRISL in 2008 for providing services to the arm of the Iranian military that oversees Iran's ballistic missile programme.