When Obama explained to a bemused world audience that it was the US Congress that had drawn a red line with respect to Syrian use of chemical weapons he cited the "Syria Accountability Act". That presumably is a reference to the Syria Accountability and Lebanese Sovereignty Restoration Act (SALSRA) of 2003 (text):
"First of all, I didn't set a red line," said Obama. "The world set a red line. The world set a red line when governments representing 98 percent of the world's population said the use of chemical weapons are [inaudble] and passed a treaty forbidding their use, even when countries are engaged in war. Congress set a red line when it ratified that treaty. Congress set a red line when it indicated that in a piece of legislation entitled the Syria Accountability Act that some of the horrendous things happening on the ground there need to be answered for.
Well, Congress used SALSRA to exhort Syria to do all manner of helpful but unlikely things per this CRS summary:
Syria Accountability and Lebanese Sovereignty Restoration Act of 2003 - (Sec. 3) Declares the sense of Congress that the Government of Syria should immediately and unconditionally halt support for terrorism, permanently and openly declare its total renunciation of all forms of terrorism, and close all terrorist offices and facilities in Syria, including the offices of Hamas, Hizballah, the Popular Front for the Liberation of Palestine, and the Popular Front for the Liberation of Palestine-General Command.
Declares the sense of Congress that the Government of Syria should: (1) immediately and unconditionally stop facilitating transit from Syria to Iraq of individuals, military equipment, and all lethal items, except as authorized by the Coalition Provisional Authority or a representative, internationally recognized Iraqi government; (2) cease its support for "volunteers" and terrorists who are traveling from and through Syria into Iraq to launch attacks; (3) undertake concrete, verifiable steps to deter such behavior and control the use of territory under Syrian control; and (4) immediately declare its commitment to completely withdraw its armed forces, including military, paramilitary, and security forces, from Lebanon, and set a firm timetable for such withdrawal.
Declares the sense of Congress that: (1) the Government of Syria should halt the development and deployment of medium- and long-range surface-to-surface missiles and cease the development and production of biological and chemical weapons; and (2) the Governments of Lebanon and Syria should enter into serious unconditional bilateral negotiations with the Government of Israel in order to realize a full and permanent peace.
And having made these demands, Congress naturally included an "or else". But despite Obama's rhetoric, the "or else" did not include a threat of military action:
(Sec. 5) Sets forth the following penalties against Syria until the President determines and certifies to Congress that Syria meets the requirements of this Act.
Directs the President to prohibit the export to Syria of any item, including the issuance of an export license, on the United States Munitions List or Commerce Control List of dual-use items in the Export Administration Regulations.
Requires the President, at the same time, to impose two or more of the following sanctions: (1) prohibit the export to Syria of U.S. products (other than food and medicine); (2) prohibit U.S. businesses from investing or operating in Syria; (3) restrict Syrian diplomats in Washington, D.C., and at the United Nations in New York City, to travel only within a 25-mile radius of Washington, D.C., or the United Nations headquarters building, respectively; (4) prohibit aircraft of any air carrier owned or controlled by Syria to take off from, land in, or overfly the United States; (5) reduce U.S. diplomatic contacts with Syria (other than those required to protect U.S. interests or carry out the purposes of this Act); and (6) block transactions in any property in which the Government of Syria has any interest, by any person, or with respect to any property, subject to U.S. jurisdiction.
Authorizes the President to waive such sanctions for one or more six-month periods if the President determines that it is in the national security interest of the United States to do so and reports his reasons to Congress.
Syrian diplomats might be restricted from visiting Disneyland or the Grand Canyon, but cruise missiles don't get a mention.
So that was a pretty pale red line Congress drew back in 2003. However, it was not so pale that George Bush did not use his signing statement to explain that he would maintain the perogatives of the Executive Branch:
Section 5 of the Act purports to impose upon the President requirements to take certain actions against Syria unless the President either determines and certifies to the Congress that the Government of Syria has taken specific actions, or determines that it is in the national security interest of the United States to waive such requirements and reports the reasons for that determination to the Congress. A law cannot burden or infringe the President's exercise of a core constitutional power by attaching conditions precedent to the use of that power. The executive branch shall construe and implement section 5 in a manner consistent with the President's constitutional authority to conduct the Nation's foreign affairs and as Commander in Chief, in particular with respect to the conduct of foreign diplomats in the United States, the conduct of United States diplomats abroad, and the exportation of items and provision of services necessary to the performance of official functions by United States Government personnel abroad.
My approval of the Act does not constitute my adoption of the various statements of policy in the Act as U.S. foreign policy. Given the Constitution's commitment to the Presidency of the authority to conduct the Nation's foreign affairs, the executive branch shall construe such policy statements as advisory, giving them the due weight that comity between the legislative and executive branches should require, to the extent consistent with U.S. foreign policy.
Or put another way, however pale that line may have been, George Bush claimed an encroachment on Executive responsibility and erased it.