Update, June 15, 2015: The House of Representatives has rejected President Obama’s push to expand trade negotiating power, likely preventing the sweeping Trans-Pacific Partnership from becoming law anytime soon. Read more from the New York Times.

This is a guest post by Sarah Jackson, former Earthjustice communications intern. Sarah is a recent graduate of San Francisco State University where she studied international relations. She is now working on Capitol Hill in Washington, D.C.

The fight against the largest trade deal since the North American Free Trade Agreement (NAFTA) will come to a head tomorrow afternoon, but you’ve likely never heard of it. That’s the point. The deal—a trade agreement between the United States and 11 Pacific Rim nations—has been crafted in secret over the past seven years.

Known as the Trans-Pacific Partnership, or TPP, it’s been cast as “NAFTA on steroids” by environmentalists, labor activists and supporters of limited government who have united in a broad coalition against the bill.

Despite these concerns, President Obama is seeking to fast-track the TPP, the largest trade deal in U.S. history, without a debate in Congress. If the president gets fast-track authority, whatever deal his trade representatives send to Congress will be put to a straight up or down vote, with no room for amendments.  In April, supporters of the TPP in the Senate introduced a bill guaranteeing fast-track trade authority, along with a matching bill in the House of Representatives. The Senate passed its bill in late May, and after weeks of tense negotiations, Republicans in the House have scheduled a final vote on their version for tomorrow.

The TPP covers a wide range of issues, including environmental safeguards, intellectual property rights, labor and access to medicines. Unfortunately, none of the 29 chapters of the deal under negotiation has been made public—until recently.

Thanks to leaked documents we know one aspect of the deal grants sweeping powers to transnational corporations that could reshape our justice system and endanger local, state and federal laws, including bans on fracking. Under the deal, foreign corporations could sue the U.S. government for regulations they say would dampen their investment “expectations,” a.k.a. profits. These cases would not be decided in court, but instead through secretive international arbitration, and the results would be automatically enforceable in U.S. courts.

Corporations such as Exxon Mobil and Dow Chemical have already used similar processes under other trade agreements to bring hundreds of cases against almost 100 governments. They’ve challenged laws that require health warnings on cigarettes and ban the use of toxic chemicals, to name a few.

Critics are concerned that, if passed, the TPP could be a way for the fossil fuel industry to go after fracking bans. New York Attorney General Eric Schneiderman, who represents the only state to ban fracking (so far), wrote that the TPP is “particularly worrisome” to those states with robust laws to protect public welfare.  

His fears aren’t unfounded. Canada is currently in the midst of a lawsuit in which oil and gas developer Lone Pine Resources Inc. is suing the government for banning fracking in Quebec under NAFTA’s investor-state dispute settlement clause, the same provision that has caused uproar over the TPP.

Foreign governments aren’t the only ones that can be sued. In 1999, California placed a ban on the chemical MTBE, found in gasoline, following reports of poisoned groundwater. Methanex, the Canadian company that developed the chemical, challenged the ban  in a suit for $970 million under the same clause in NAFTA. In 2005, the private tribunal finally dismissed the case after six years of litigation.

Earthjustice, along with other leading environmental and science organizations, has called on members of Congress to oppose fast-track trade authority for President Obama. Fast-tracking the TPP would prioritize corporate power over public demands, undermine local and state courts and threaten the advances we’ve made on environmental regulation. With so much at stake, Congress can’t afford to pass this trade deal without making time for meaningful—and transparent—debate.