Judging from press reports, when Congress returns from its August recess in early September, the United States military will have been bombing "Islamic State" fighters in Iraq for a month, with a broader set of missions than originally advertised, and with plans to continue bombing for months.

The United States Constitution and the 1973 War Powers Resolution require that such a war be authorized by Congress in order to continue. We cannot accept that such major decisions about the use of our power and resources, putting U.S. soldiers at risk and shaping the perceptions of the world about us by shedding the blood of foreigners that we don't know, be made indefinitely behind closed doors by executive fiat.

As Representative Jim McGovern said on August 8 when the strikes began:

These strikes do involve the United States directly in hostilities, regardless of how limited they are and regardless of whether there's a humanitarian purpose involved... If these operations are continuing when Congress returns in September, then Congress needs to take action to authorize them.

On July 25 -- two weeks before the U.S. bombing of Iraq began -- the House overwhelmingly passed 370-40 an amendment offered by McGovern, insisting that Congressional authorization precede any "sustained combat role" in Iraq for U.S. forces. Currently it seems that a "sustained combat role" for U.S. forces is exactly what the Administration and the Pentagon are planning.

Ninety-eight percent of the Democrats voting and 83 percent of the Republicans voting supported the McGovern amendment.

In Congress and public opinion, there are, broadly speaking, three camps right now regarding the airstrikes the U.S. is conducting in Iraq. There is a camp cautiously supporting the President's actions so far, but worried about mission creep and seeking to contain further escalation; there is a camp opposed to the President's actions so far because they do not want to see any U.S. military action in Iraq right now at all; and there is a camp that supports the President's actions so far but wants the U.S. to do much more, and is pressing the President to do much more.

Whatever one thinks of the President's actions so far, it does not seem likely that there will be a majority in Congress in the near future to force the withdrawal of U.S. military forces. But there might well be a majority in the near future to do two things:

- Insist that a military campaign that goes on for months needs explicit Congressional authorization, as required by the Constitution and the War Powers Resolution; and

- try to establish limits on the military campaign through such an authorization.

One way to try to establish limits is to try to specify in the resolution exactly what mission(s) the authorization is for. This is a good thing to try to do; it will force the Administration to articulate more clearly what the mission(s) are.

But that the track record of trying to constrain the President -- any President -- in this way is very poor. The 2002 Iraq AUMF was used as authority for a war that continued until the withdrawal of U.S. troops in December 2011, long after Saddam Hussein was executed, long after his "weapons of mass destruction" were found to be non-existent, his government was destroyed, and his army was disbanded.

The 2001 "global war on terror" AUMF passed after the September 2001 attacks was dangerously overbroad, as Representative Barbara Lee correctly warned at the time. But even the already overbroad 2001 AUMF was dramatically expanded through interpretation by the Bush and Obama Administrations with Congressional acquiescence, creating the category of "associated forces" to al Qaeda as targets for U.S. military force, although this concept did not appear in the resolution.

Far and away the most successful tool that Members of Congress have used since 2001 to push for ending wars that have started has been to demand the establishment of a timetable for ending them.

This suggests that Congress should consider giving its authorization for war in Iraq an expiration date. This would force Congress to reconsider the war in the future if it continued; it would force the President to make his case in the future for continued war; it would force the nation to reflect on the claims that were made when force was authorized and how these claims turned out before renewing the authorization for force.

There is no successful legal precedent yet that I am aware of for giving a war authorization an expiration date. But in other legislation, it is normal for things to expire, so that they have to be explicitly renewed. The Patriot Act had an end date. That ensured that Congress would have to revisit the question of authorizing expanded government surveillance in the future if the Administration wanted to continue having such expanded authority. There is no legal reason that a war authorization could not have an end date, ensuring that Congress would have to consider the issue again in the future in order for the war to continue.

And there is a significant, recent political precedent for the idea that a war authorization should "sunset." In May, Rep. Adam Schiff offered an amendment -- supported by many civil liberties and peace groups -- to make the 2001 AUMF expire in a year, so that Congress would have to consider a new authorization of force for the "war" formerly known as the "global war on terror." The amendment was narrowly rejected 233-191. As recently as May, 191 Members of the House -- 164 Democrats and 27 Republicans -- voted for the idea that an authorization of force can expire and have to be renewed.

A lot can happen between now and when Congress comes back into session in September. But we can say now that it is plausible that Congress could pass such a limitation in September, and that this might be the strongest limitation that Congress can pass in September.