OK, I don’t normally quote Middle East Progress but they have a good summary of Iran’s National Security Framework- who controls what within Iran:

June 16, 2009
Supreme Leader
• Designated the political and religious leader of the Islamic republic.
• Controls all critical foreign policy decisions.
• Appoints the six religious members of the Council of Guardians.
• Appoints the head of the judiciary, leader of the state-run media and the top military officials.
• Commands the armed forces, decides when to mobilize the military and is the only person who can declare war and peace.
• Possesses final authority over all decisions and recommendations made by the Supreme Council for National Security.

Guardian Council of the Constitution
• A 12-member group, 6 theologians and 6 lay jurists that can veto laws and treaties passed by the legislature.
• Vets candidates for the presidency, legislature and Assembly of Experts.

President
• Holds the second-highest office after the supreme leader.
• Highest-elected official in Iran and holder of the most visible public office.
• Presides over the Supreme Council for National Security, but cannot veto its decisions; signs treaties approved by the legislative body; and accepts the credentials of ambassadors.
• Heads the executive branch and is responsible for appointing cabinet ministers.
• All candidates pre-screened by the Council of Guardians after declaring candidacy.

Supreme National Security Council
• Runs the country’s security policy framework as determined by the supreme leader.
• Composed of the heads of the executive, legislative and judiciary branches, as well as military leaders and other senior officials.

Assembly of Experts
• Directly-elected group of 86 clerics charged with electing and supervising the supreme leader. All have to possess religious authority to issue fatwa.

Majlis
• The 290-seat legislative body approves all treaties and international agreements.

Expediency Discernment Council
• Advises the supreme leader on policy.
• Resolves disputes between the Majlis and the Council of Guardians.

Islamic Revolutionary Guard Corps
• Established to safeguard the revolution; reports directly to the supreme leader.
• Former members occupy top political positions in the Ahmadinejad government.
• Operates separately from the regular armed forces and maintains parallel branches, including ground, air, naval, intelligence and strategic operations.
• Possesses control of Iran’s strategic rockets and missiles.

The Quds Force
• Responsible for supporting strategic operations outside the country for the IRGC.
• Labeled a terrorist organization by the Bush administration in 2007.
• Accused by the United States of supplying munitions and other military support to Hezbollah, Hamas, Islamic Jihad, the Taliban in Afghanistan and militants in Iraq.

Armed Forces
• Responsible for guarding the independence and territorial integrity of the country.

Links are provided at the website:
middleeastprogress.org