Just two months ago, when President Obama nominated the architect of his vast killing program, John Brennan, to be CIA Director, the Obama Administration was doing its best to keep almost all of its made-up rules for the killing program effectively locked away in a hermetically sealed black box. But in nominating Brennan, the president was waving a red flag at Congress, all but taunting Congress on just how little Congress and the American people know about hidden rules, which allow "informed, high-level officials" to kill people away from any battlefield, even American citizens.

But thanks to a bipartisan coalition from the right and the left—all concerned about the Constitution and the rule of law--that is no longer the case. Sure the black box hasn't been smashed yet, but because of committed activists, courageous senators, and public outrage, Congress has once again started to assert its role of watchdog over the White House's most secretive program.

On Capitol Hill, there was no one who shined the light more brightly on this fight for constitutional checks and balances and oversight of the Obama administration's killing program than the Republican senator from Kentucky, Rand Paul. As a result of Sen. Paul's historic filibuster this week, Americans got two wins: the Obama administration said it was unconstitutional to use an armed drone within the United States in the absence of a Pearl Harbor-style attack. But more importantly, he woke up Americans and the world to the breathtakingly broad claims asserted by the Obama administration to unilaterally kill someone away from a battlefield without due process.

In the filibuster's wake, a truly bipartisan coalition in Congress and among the public has emerged to demand that President Obama turn over to Congress and the American public its legal opinions justifying his vast killing program. These secret, made-up rules have been used as legal cover to kill as many as 4,700 people, including four American citizens, Sen. Lindsey Graham, R-S.C, revealed recently. Maybe even more importantly, a rising tide of "checks and balances Republicans" flooded the Senate floor as nearly every Republican face of the future in the Senate came down to "Stand with Rand" on this key issue. The Senate will never be the same.

In early February, Senator Ron Wyden and ten members of both parties kicked off the push for accountability by writing to the president to demand the legal memos for the vast killing program. Things really started to catch fire when NBC's Michael Isikoff, in early February, obtained a leaked white paper of the Department of Justice's legal reasoning behind the Obama administration's claim that it can kill an American citizen without any due process when "a high-level official" deems that person a terrorist threat to the United States. When Isikoff obtained the document, the ACLU's Jameel Jaffer gave his verdict on it: "a chilling document," which he followed up with a blog post analyzing the document and noted that "[s]ome of the white paper's key legal arguments don't stand up to even cursory review."

Since then, key senators of both parties kept the White House on the defensive, and rightly so, over its secret killing program. There have been results:

The public pressure has led President Obama to make a State of the Union promise to be more forthcoming about the targeted killing program.

This week, Attorney General Eric Holder said the American people can expect President Obama to address them directly on the issue of the unlawful killing powers he has claimed.

The White House finally released several of the legal memos justifying the program to the Senate and House Intelligence Committees.

For the first time ever, two congressional oversight hearings.

A disavowal of any authority to use armed drones domestically.

The chairmen of the Senate and House Judiciary Committees have told the Obama administration that they may subpoena the memos if the administration doesn't turn them over soon.

Despite these pushes for more robust congressional oversight, there is no substitute for providing all the legal opinions to both Congress and the American people. More importantly, no one in Congress or among the American people should accept anything less than being able to read for themselves what the president is claiming that he can do, even to American citizens. The American people, both left and right—and everyone in-between—have real concerns over the Obama administration's vast killing program. This development should be nurtured and expanded, and the ACLU will do whatever it can to make this coalition a powerful majority.

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