A bill that looks likely to pass the Senate would drastically reduce the ability of states to regulate toxic chemicals, according to a leading environmental law firm.

Legislation proposed Tuesday by Sens. Tom Udall (D-N.M.) and David Vitter (R-La.), with the backing of 16 bipartisan cosponsors, “represents a giant step back,” Earthjustice stated in a letter.

Andrea Delgado, a legislative representative for the group, said Thursday that the measure has been put forward, in a roundabout way, due to the weakness of the Toxic Substances Control Act—but that it does not seek, on the whole, to strengthen environmental and consumer safety protections.

“Over time, many states have enacted their own chemical regulations to fill the void,” she said, referring to the landmark Ford-era law and its deficiencies. “And now, the bill just proposed in the Senate–deceitfully guised as ‘reform’–would undercut state laws that have proven effective in protecting American families from toxic chemicals.”

Despite the apparent attack on state’s rights, Republicans have faithfully queued up to support the bill. Backers, to date, include Environment and Public Works Committee chair Jim Inhofe (R-Okla.) and eight members of his party’s caucus.

The legislation has been referred to Inhofe’s committee, which contains six cosponsors from both parties.

When it was introduced this week, Udall and Vitter hailed the bill as the result of a two-year long compromise, with the former touting its regulatory credentials. The Hill reported that it would strip from law a requirement that stopped the Environmental Protection Agency from banning asbestos, raise the cost of fines, and create new EPA safety review processes.

But The Hill also noted that the environment committee’s ranking member, Sen. Barbara Boxer (D-Calif). “has been a leading opponent of the reforms”–a scenario that indicates green groups like Earthjustice will labor hard to stop the bill as it winds its way through Congress.

Andy Igrejas, the director of Safer Chemical, Healthy Families, a public interest coalition, also described the legislation as problematic.

The group said in a letter to Senators that it would create a two-tier system of regulation that would allow substances deemed “Low Priority” to escape examination. It also noted that the legislation would “weaken the “EPA’s ability to ensure that an imported product does not contain a restricted chemical” and force the agency “to jump through additional regulatory hoops to regulate the chemical in a product.”

“In its current form it would not make a big dent in the problem of toxic chemical exposure and would even do some harm by restraining state governments,” Igrejas said. He did, however, note that the legislation has “made some positive changes,” and that his group intends “to work with Senators from both parties to make the needed improvements.”