Why and How Is the US Blockading Iranian Ports in the Strait of Hormuz?

The United States has initiated a naval blockade of maritime traffic entering and exiting Iranian ports, aiming to limit Tehran’s ability to profit from oil exports. This move is part of a broader effort to exert economic pressure on Iran, which Washington claims has effectively closed the Strait of Hormuz to ships from other regions in response to recent US-Israeli strikes.

Legal and Strategic Context

According to the US Navy Commander’s handbook from 2022, a blockade is defined as a “belligerent operation to prevent vessels and/or aircraft from entering or exiting specified ports… under the control of an enemy state.” However, the UN’s International Maritime Organisation disputes this, stating that no nation holds a legal right to restrict shipping in straits used for international transit. Secretary-General Arsenio Dominguez emphasized to the BBC that “there is still no legal basis in international law to block any strait used for international navigation.”

“We’re not going to let Iran make money on selling oil to people that they like and not people that they don’t like,” said Donald Trump, highlighting the goal of ensuring “all or nothing” passage through the crucial shipping channel.

Operations and Positioning

While the exact locations of US naval forces remain undisclosed, satellite imagery from 11 April reveals the USS Abraham Lincoln aircraft carrier stationed at the eastern edge of the Gulf of Oman—approximately 200km (124 miles) south of the Iranian coast. This proximity suggests a strategic focus on monitoring ships departing Iranian ports before intercepting them in the open Indian Ocean. Two additional vessels visible in the imagery are suspected to be part of the Lincoln’s carrier strike group, though their identities remain unspecified.

US Central Command (Centcom) has stated that humanitarian shipments, such as food and medical supplies, will be allowed through the strait provided they undergo inspection. The military is also poised to destroy mines attributed to Iran, which the administration claims were deployed in the region. Despite these measures, no confirmed interceptions or seizures of vessels have been reported yet.

Risks and Responses

Iran has denounced the blockade as “piracy,” vowing retaliation by targeting Gulf state ports. Meanwhile, international law experts note that the US, Israel, and Iran may be classified as belligerents in this context, enabling the US to justify the blockade under the law of naval warfare. The operation’s success hinges on its ability to intercept Iranian-linked ships without triggering broader conflict, as seen in tracking data showing four such vessels have already crossed the strait despite the blockade.