New List-Based Sanctions on Syria
On April 29, 2011, the President signed an Executive Order blocking the property of five designated persons with respect to human rights abuses in Syria.  The Order blocks all property and interests in property within the jurisdiction of the United States of Mahir al-Asad, Ali Mamluck, Atif Najib, the Syrian General Intelligence Directorate and the Islamic Revolutionary Guards Corps-Qods Force. The Order also blocks the property of entities owned or controlled by these persons.
The White House issued the following descriptions of the designated persons, conspicuously naming President Asad's brother, but omitting the Syrian president himself:
Mahir al-Asad: The brother of Syrian President Bashar al-Asad and brigade commander in the Syrian Army's 4th Armored Division, who has played a leading role in the Syrian regime's actions in Dar'a, where protesters have been killed by Syrian security forces.
Atif Najib: A cousin of Syrian President Bashar al-Asad, Najib was the head of the Political Security Directorate (PSD) for Dar'a Province during March 2011, when protesters were killed there by Syrian security forces.
Ali Mamluk: Director of Syria's General Intelligence Directorate (GID).
Syrian General Intelligence Directorate (GID): The overarching civilian intelligence service in Syria. The GID represses internal dissent and monitors individual citizens. It has been involved in the Syrian regime's actions in Dar'a where protesters were killed by Syrian security services.
Iranian Islamic Revolutionary Guard Corps - Qods Force (IRGC-QF): Iran is providing material support to the Syrian government related to cracking down on unrest in Syria. The conduit for this Iranian material support to the Syrian General Intelligence Directorate is the IRGC-QF. Despite the Government of Iran's public rhetoric claiming revolutionary solidarity with people throughout the region, Iran's actions in support of the Syrian regime place it in stark opposition to the will of the Syrian people. The IRGC-QF is a branch of the Islamic Revolutionary Guard Corps, which is considered the military vanguard of Iran. The IRGC-QF was designated by the Treasury Department in October 2007 for providing material support to terrorist groups around the world, including the Taliban, Lebanese Hizballah, Hamas, Palestinian Islamic Jihad and the Popular Front for the Liberation of Palestine-General Command.
Since 2004, the United States has imposed sanctions on Syria: (1) blocking the property of designated persons; (2) prohibiting exports of items on the United States Munitions List or on the Commerce Control List to Syria; (3) prohibiting, with certain exceptions, the Secretary of Transportation from authorizing any air carriers owned or controlled by Syria from providing foreign air transportation; and (4) requiring that the Secretary of Transportation, with certain exceptions, prohibit all takeoffs and landings in the United States by any air carrier owned or controlled by Syria when engaged in scheduled international air services. 
The United States has since expanded sanctions against Syria. In 2006, it blocked the additional persons identified as involved in the planning, sponsoring, organizing or perpetrating of the assassination of former Lebanese Prime Minister Rafiq Hariri and others.  In 2008, additional Syrian officials were designated and their property blocked as a result of their alleged role in contributing to public corruption in Syria and undermining the stability of Iraq.