Recently, 450 U.S. environmental groups sent Congress a strong message: Vote down the Trans-Pacific Partnership (TPP), the largest proposed trade deal since 1994’s North American Free Trade Agreement (NAFTA).

The environmental groups, a collective of landowner, indigenous rights and other allied organizations expressed their opposition to TPP by penning a letter to Congress, urging members to vote against the controversial trade agreement.

“We strongly urge you to stand up for healthy communities, clean air and water, Indigenous peoples, property rights, and a stable climate by committing to vote no on the TPP and asking the U.S. Trade Representative to remove from TPP any provision that empowers corporations to challenge government policies in extrajudicial tribunals,” said the letter, which was signed by organizations such as Sierra Club, Indigenous Environmental Network, Bold Alliance, SustainUS and Friends of the Earth.

The TPP has been under negotiation between partner countries Australia, Brunei, Canada, Chile, Japan, Malaysia, Mexico, New Zealand, Peru, Singapore, Vietnam and the U.S. for more than five years. The environmental groups say that a bad trade deal will bring about the further extraction of fossil fuels, despite the desires or even regulations to the contrary that may exist via local governments.

The groups opposing the TPP believe that such unwanted oil and gas extraction will be allowed to supersede local, regional or even national no-drill ordinances by way of Investor-State Dispute Settlements (ISDS), a controversial element of the TPP that’s burrowed deep within the 29-chapter trade deal. In the letter, environmental groups warn Congress against dangerous ISDS provisions, stating they would allow multinational oil and gas companies to sue nations in private tribunals to overturn laws prohibiting hydrocarbon development.

“Property rights are under constant threat by big corporations,” says Jane Kleeb, president of Bold Alliance. “The TPP will create a scenario for landowners where they are at the mercy of big oil and big gas to do whatever they want with our land and water using secret courts and backroom deals.”

The groups warn that ratifying the TPP, as is, would pose a major threat to any current or future restrictions on fossil fuel pipelines, oil and gas extraction or fracking on U.S. public lands.

With 50,000 active wells in Colorado, the centennial state is one of the nation’s largest producers of oil and gas.

In May, the Colorado Supreme Court struck down Longmont’s voter-approved fracking ban and Fort Collins’ moratorium, ruling that the local prohibitions interfered with the state’s goal of maximizing oil and gas production. Boulder County’s five-year moratorium on issuing new drilling permits was also affected by the Supreme Court’s decision. It has been replaced by a new six-month moratorium as a result.

According to critics of the TPP, local laws in Colorado such as bans, moratoriums or even local air and water standards could be overturned by way of the ISDS.

In TPP tribunals, oil and gas companies couldn’t force Colorado or its communities to rescind fracking bans. They could, however, attempt to collect massive fines from the federal government for lost profits due to local regulations of cities, counties or states that inhibit unbridled oil and gas extraction in any way. We need look no further than NAFTA for an example of what the TPP will likely bring. TransCanada filed a $15 billion grievance in NAFTA’s version of ISDS against the U.S. for rejecting the Keystone XL tar sands pipeline in November 2015.

“Oil companies want to sue because they could be awarded millions — in some cases billions — of dollars in damages,” says Bill Waren, trade analyst at Friends of the Earth. “It is an effective way to thwart local action because it creates powerful incentives for the national government to impede local action in order to limit its liability.”

The International Trade Administration anticipates that Colorado will become a catalyst for foreign exports, serving as a model for increasing direct foreign investments in the state. In 2014, 47 percent of Colorado’s exports went to countries participating in TPP negotiations, and a new kind of Colorado export may be on the horizon. The oil and gas industry has made no secret of its plans to use TPP to increase its exports of oil and liquefied natural gas.

The environmental groups also challenge that TPP’s expansion of ISDS liability would create a new threat. They believe oil and gas companies would no longer be forced to protect communities from other fossil fuel hazards such as oil trains and refineries. And ISDS provisions could also constrain how Colorado spends its tax dollars, limiting the state’s conservation efforts as well as the state’s ability to provide public goods and services. Colorado’s energy conservation, renewable energy efforts, transportation infrastructure and any upcoming minimum wage hikes would all be potentially vulnerable to ISDS suits.

“TPP tribunals could rule against the setback and community control initiatives and tell the state to abandon the decision of the people or require fines to be paid by the federal government if the companies convince the tribunals that they have lost profits as a result of the initiatives,” says Carolyn Bninski, staff member with the Rocky Mountain Peace and Justice Center.

Rep. Jared Polis (D-Boulder) is one of the only Congressional members claiming to still be undecided on the TPP. He has repeatedly claimed that no corporate court provisions exist within the TPP, and the trade agreement poses no threat to Coloradans. He insists, despite his having played a key role in not allowing local control over oil and gas extraction initiatives to make the ballot in 2014, he is a supporter of local control and believes that communities should be allowed to ban fracking and other extraction activities.

“It’s a shame that our own courts stripped this right away from Colorado’s local governments this last May,” Polis says. “In fact, I submitted an amicus brief in that lawsuit that argued for the rights of local communities.”

Polis says he was successful in getting language in the Trade Promotion Authority that states instructions from Congress to the Obama Administration that nothing in the TPP is allowed to prevent local and state governments from enacting laws to protect public health, safety and the environment.

“In Colorado, as well as other states, that, of course means, that the TPP thankfully cannot restrict new setbacks and local control of fracking. Our problems with the Colorado courts, however, remain and hopefully Colorado voters will have the opportunity to change the law soon,” Polis says.

Despite this effort by Polis, it is still unclear if Obama or any other signatory to the trade agreement would be bound by such “instructions.”

And, as mentioned earlier, the TPP does not restrict the passage of local laws. It simply allows a corporation to seek damages against the Federal government due to those local laws which would then most likely cause the federal government to exert its power through the Environmental Protection Agency, Food and Drug Administration or other regulatory agencies to challenge local laws as being contrary to federal regulations, which would ultimately result in the local regulations being overturned. Allowing local laws to be made does not mean that the federal government could and would not subsequently exert its power to remove them.

The groups fighting against the TPP say time is running out … for all of us.

“Scientists tell us that we need to keep well over 80 percent of the world’s fossil fuels in the ground,” Waren says. “No one can be a climate champion and support trade deals like these, which provide polluters with a new corporate bill of rights and impede our ability to keep fossil fuels in the ground.”

In short, the TPP is unfavorable to environmental groups for putting climate policies at risk and weakening environmental protections. Polls show that 60 percent of Colorado voters have an unfavorable opinion of this trade agreement.

“Americans deserve land security and it starts with saying no to the TPP handout to big corporations,” Kleeb says.

Congress isn’t expected to ratify the TPP agreement until a lame duck session after the election There’s still time to submit proposals to your representative.