Senate Republicans’ long-awaited version of a key law aimed at protecting women from domestic violence was finally unveiled this week and promptly denounced by tribal advocates.

The bill, introduced by Republican Sen. Joni Ernst of Iowa, curtails powers tribal courts gained when the Violence Against Women Act was last reauthorized by Congress in 2013 by imposing new restrictions and requirements.

It contrasts sharply with the House version of the bill, which passed with strong bipartisan support in April and would authorize Maine’s tribal courts to try people accused of domestic violence, stalking and trafficking on their reservations even if they aren’t Native Americans. The issue has been a flashpoint between the tribes and state authorities over the scope of tribal authority in Maine.

Other federally recognized tribes have had this authority under the passage of the 2013 renewal of the law, but Maine’s tribes were not included because then-Attorney General Janet Mills objected, citing provisions of the 1980 federal law that settled the tribe’s land claims to more than half of Maine. This law says no federal Indian law applies to Maine’s tribes if it “affects or preempts” Maine’s jurisdiction, unless Congress explicitly says otherwise in the law’s text.

In April, the House passed its version of the reauthorization bill including language introduced by Democratic Rep. Chellie Pingree of Maine extending its authority to Maine tribes and Alaska native people. The vote was 263-158, with 33 Republicans joining nearly every Democrat in support. Since then, the Penobscot Nation – which has a widely respected tribal court and has sought to have authority over these domestic violence cases – has awaited Senate action on the measure.

But on Wednesday Ernst blocked an effort by Democratic Sen. Diane Feinstein of California to hold a vote on a bill modeled on that passed by the House.

“Why on earth would we introduce a piece of legislation that will not make it through this body?” Ernst said at the time. Ernst’s spokesman – Brendan Conley, who worked for Maine’s Rep. Bruce Poliquin until his election defeat a year ago –  did not respond for a request for comment.

Instead, Ernst unveiled a Republican version of the bill that would weaken the ability of all tribal courts to prosecute crimes by non-tribal members who harm tribal women on reservations. The bill allows such suspects to appeal to federal court without first exhausting tribal court remedies and removes tribal nations’ sovereign immunity, making them vulnerable to civil rights suits by those they are trying to prosecute. It also directs the U.S. attorney general to audit the tribal courts to ensure they are in compliance.

The National Indigenous Women’s Resource Center, a group that lobbies on behalf of tribal women and children, blasted Ernst’s bill, saying it would effectively roll back all the gains made in the 2013 version of the law and leave tribal women more vulnerable to abuse.

“Despite the fact that the implementation of VAWA 2013 has been a success – both for the protection of victims in our communities as well as the due process rights of non-Indian defendants – Ernst’s bill is based on the assumption that the protections for Native victims in VAWA 2013 must be rolled back because tribal courts are not capable of fairly administering justice,” the group’s counsel, Mary Kathryn Nagle, said in a statement. “Since 2013, tribes have clearly demonstrated this assumption to be false. Tribal courts prosecuting non-Indian defendants already provide the same – if not more – due process rights than state and federal courts.”

Ernst’s bill includes language that explicitly says the law will apply to Maine tribes. Federal laws that do not include such language have been challenged by Maine authorities under their interpretation of the 1980 Maine Indian Claims Settlement Act.

Asked for comment on Ernst’s bill, Pingree issued a written statement in which she said: “I hope to see the Senate move forward on the House-passed version of the bill soon.”

Neither of Maine’s senators, Republican Susan Collins and independent Angus King, were among the Ernst’s bill’s 10 initial co-sponsors.  King – who was in Nova Scotia attending the Halifax International Security Forum and unavailable for comment – is among 46 Democrats and independents who are co-sponsoring the competing bill introduced by Feinstein.

A spokeswoman for Collins, Annie Clark, said via email that the senator wanted a reauthorized VAWA to ensure perpetrators of domestic violence and sexual assault are held accountable, regardless of whether their crimes were committed on tribal or non-tribal lands. “While it is unfortunate that effort to craft a bipartisan VAWA reauthorization broke down, she is following the committee process closely and is hopeful that a compromise can be reached.”

Penobscot tribal ambassador Maulian Dana and Rep. Jared Golden, the Democrat representing Maine’s 2nd District, could not be reached for comment.

National surveys have shown that Native American women are twice as likely to have been victims of rape or sexual assault than other Americans, and that roughly two-thirds of the perpetrators of these crimes were not Native Americans. They are also significantly more likely to have been stalked and assaulted.

In many parts of the country, tribal police and courts were not allowed to pursue non-Native Americans who attacked women on reservations until changes were made to the Violence Against Women Act in 2013, even if the perpetrators were living there and married to Native American spouses.

Under VAWA, tribal courts that meet Department of Justice guidelines to ensure due process were allowed to try certain types of domestic violence cases against people who aren’t Native Americans. The Department of Justice initially designated the Penobscot Nation’s court to serve as one of six pilot projects, but Maine blocked the move, citing the 1980 Maine Indian Claims Settlement Act.

In the near term, only the Penobscot Nation would be affected by the legal changes. The Passamaquoddy tribe has a court but lacks its own appellate body and other Justice Department requirements, while the Houlton Band of Maliseets and the Aroostook Band of Micmacs do not have courts.