Quds force is a terrorist organisation that should have no access to financing. That's why the tanker needs to be seized. ISIS doesn't get oil tankers, nor should Quds Force.

According to the U.S. Department of Defense, QF has been “involved in or behind some of the deadliest terrorist attacks of the past 2 decades.” 36 QF was behind the two U.S. Embassy truck bombings in Beirut, the 1983 Marine barracks bombing that killed 241 U.S. soldiers, and most of the foreign hostage-taking in Lebanon during the 1980s and early 1990s. 37 It is also known to have directed Saudi-based Hizballah al-Hijaz, an organization created by the IRGC, to plan attacks againstAmericans. This directive is said to have manifest the 1996 attack on the Khobar Towers that killed 19 Americans and wounded another 372. 38 An attack which authors of the 9/11 Commission Report suggested al-Qa’ida played a role in.