This week, Congress is scheduled to vote on the administration’s three-month-old request for $500 million to train and equip a reported 6,000 fighters for Syria’s so-called “moderate” opposition.

The rebels’ primary objective is to overthrow the dictatorial Syrian government, not defeat other regime challengers including the brutal Islamic extremist group ISIS. Nevertheless, following the “Islamic State’s” expansion into Iraq, President Barack Obama has recharacterized and repackaged his proposal as a key component of his anti-ISIS strategy. “We must strengthen the opposition as the best counterweight to extremists like ISIL,” he has told the nation. In the same speech he also envisioned systematic air strikes “against ISIL in Syria.” From these two statements it would be only a short step to unleashing American air power against Syrian Government forces that threatened our “counterweight.” Yet that is precisely the course of action that the administration proposed and Congress and the country rejected one year ago when they decided that U.S. interests did not justify the risks of launching air strikes against the Iranian, Russian and Hezbollah-backed Syrian Government.

Would the administration use an anti-ISIS cover to become the air force for its Syrian rebel clients? I don’t know, but there is one very good reason for Congress and the public to practice due diligence. It is called Libya.

In February 2011, soon after longtime Western-supported dictators in Egypt and Tunisia had been ousted by popular uprisings, the Gadaffi regime in Libya violently repressed peaceful demonstrations. As the conflict quickly morphed into a raging civil war, the U.S., Great Britain and France sought to reposition themselves as supporters of the “Arab Spring” by politically embracing the Libyan revolution. In March, a U.N. Security Council Resolution authorized the use of force, but solely “to protect civilians … threatened with attack.” Consistent with that, Obama declared on television, “Broadening our military mission to include regime change would be a mistake.” But that is exactly what happened.

British and French officials who were involved in Libyan policy at the working level told me that U.S. and NATO operations were designed from early on not only to protect civilians but also to overthrow Gaddafi. According to an official report of the African Union, which was making progress in its effort to mediate a cease-fire and gradual transition to democracy, U.S. officials told an AU delegation in mid-April that any ceasefire “should also include Col. Gaddafi’s departure from power.” Yet it was not until his October 2012, during his foreign policy debate with Republican Presidential candidate Mitt Romney, that Obama explicitly acknowledged the full purpose of his Libyan policy:

“But you know … when we went into Libya and we were to immediately stop the massacre there because of the unique circumstances and the coalition that we had helped to organize, we also had to make sure that Muammar Gaddafi didn’t stay there … Muammar Gaddafi had more American blood on his hands than any individual other than Osama bin Laden. And so we were going to make sure that we finished the job.”

Practically everyone now acknowledges the self-inflicted damage caused by the U.S. and NATO’s “stretching” of the Security Council Resolution. Libya has fallen into violent chaos and Islamic extremists (including those who murdered the U.S. Ambassador) have run rampant. The undisciplined exit of arms and ethnic and Islamic fighters precipitated the takeover of half of Mali and strengthened extremism across Northwest Africa and the Middle East. NATO’s reinterpretation of the U.N. Security Council Resolution alienated Russia as well as South Africa, making them less willing to cooperate with the three permanent Western members in managing the Syrian conflict.

Were the administration to similarly stretch the language of the president’s recent counterterrorism speech and deploy air power (and even advisers) behind an expanded program of military assistance to the rebels, the consequences might be even more horrendous. Unlike Gaddafi, President Bashar Assad of Syria has strong backing from Iran, Russia and Hezbollah. A wider war over who rules Syria might develop, distracting attention from the specific threat of ISIS to the entire region. Hopes for working with Iran and Russia — against ISIS, for nuclear non-proliferation, and for eventual diplomatic settlements in Ukraine and Syria — could be dashed.

That is why it is up to Congress, before during and after consideration of the administration’s current proposal for assisting Syrian rebels, to make it crystal clear that it is not authorizing direct military intervention against the Syrian regime.

Stephen R. Weissman is a former staff director of the House Africa Subcommittee and author of “In Syria, Unlearned Lessons from Libya,”