Many details of the Trans Pacific Partnership (TPP) are still cloaked in mystery, but a trio of Senators have learned enough about them to raise concerns that the trade deal could precipitate another financial meltdown.

On Tuesday, Sens. Tammy Baldwin (D-Wis.), Ed Markey (D-Mass.) and Elizabeth Warren (D-Mass.) sent a letter to US Trade Representative Michael Froman objecting to a number of such provisions being considered by his delegation.

Most notably, the trio singled out clauses that would establish an international court that serves primarily to further the interests of multinational corporations through a process known as Investor-State Dispute Settlement (ISDS).

“The investor-state dispute settlement process permits foreign companies to bypass American courts and challenges US government policies before a panel of private attorneys that sits outside any domestic legal system,” Sens. Baldwin, Markey and Warren wrote. “And because the investor-state process is available only to investors, it gives investors a far greater ability to challenge state practices than it gives labor unions, environmental groups, or any other non-investor with an interest in a trade deal,” the three said.

ISDS provisions included in prior trade agreements like NAFTA have allowed corporations to extract large sums from governments, if these international courts deemed that a regulation violated the often opaque “minimum standard of treatment,” the senators pointed out.

According to the UN, these investor disputes are increasing. In 2012, there were nearly sixty cases brought by corporations against governments – the most ever recorded. The majority of these disputes were brought by American companies seeking to undo regulations in developing countries.

How this relates to Wall Street is that the senators fear the TPP could include “minimum standards” that would affect financial regulations in a trade deal for the first time. To justify the worries, they cited a 2006 example of an international trade court ordering the Czech Republic to pay an international bank more than $200 million, after its government declined to bailout the failing institution.

“[ISDS] provisions in the TPP would be troubling enough because they would expose a broad array of critical American financial regulations to challenge by many additional foreign companies,” the Senators wrote. They added that such measures would “strip our regulators of the tools they need to prevent the next crisis.”

Other possible TPP clauses causing the Senators heartburn were provisions regarding market access and capital controls. The Senators said such rules could “prohibit basic, non-discriminatory restrictions on predatory to toxic financial products” and “curtail certain limitations on the size or the operations of financial firms.” They may also forbid lawmakers from passing a financial transaction tax in the future – a revenue-raising volatility-controlling measure that came to prominence during the Occupy Wall Street movement.

Last month, President Obama said that the trade deal is “moving forward” and suggested it could be finalized “sometime soon,” but its ultimate fate is still uncertain. The real test comes next year when the new Congress will have to decide whether or not to grant the White House “fast-track authority” to pass TPP. If it does, lawmakers would be unable to offer amendments to change any deal finalized by the administration. But with discussions over the multilateral Pacific Rim trade deal having taken place behind closed-doors, many lawmakers appear reluctant approve either the deal, the process or both.

The Senators asked Froman to respond to their concerns by Jan. 6 of next year.

You can read the Senators letter here.