ALBUQUERQUE, N.M. (AP) – Citing concerns of tribal leaders, U.S Sen. Martin Heinrich said Tuesday he would push to broaden the scope of a federal law designed to crack down on the looting, trafficking and exporting of federally protected Native American items.

Heinrich plans to introduce legislation that would double the prison time to 10 years for violating a statute that criminalizes stealing or unlawfully removing tribal objects from reservations. Meanwhile, the proposal would allow for a two-year amnesty period for people to voluntarily return items obtained illegally.

A third piece of the legislation that Heinrich has termed the STOP Act would prohibit dealers from exporting protected Native Americans items of cultural or historical importance for tribes to international markets.

Following a wave of auctions in Paris in recent years that have placed tribal items up for bidding, some leaders have begun to argue that religious property, either stolen or sold in violation of tribal laws, has been sent to foreign auction houses by dealers seeking to bypass U.S. laws.

In most cases, the French have not been able to intervene because U.S. law does not explicitly ban American dealers and others from exporting the items, Heinrich said.

“I don’t remember a time I’ve heard from so many tribal leaders at the same time at the same place about something that is so important culturally,” he said at a news conference held in Albuquerque with pueblo leaders. “This is an issue that has touched tribe after tribe for too many years.”

The plans for the legislation come as Acoma Pueblo in western New Mexico awaits word on whether a ceremonial shield the pueblo says was stolen decades ago and sent to France for auction will be returned.

In May, EVE auction house in Paris resisted calls by top U.S. officials and pueblo leaders to halt the sale of the shield and other items, until the pueblo produced an affadavit alleging it had been taken during a break-in from an elder’s Acoma Pueblo home.

Investigations into how the shield came on the market were opened in both the U.S. and France.

“The strength of the pueblos, or any tribe across the country depends on the strength of its culture, its ceremonies and its continued belief in what is most sacred,” Gov. Kurt Riley, of Acoma Pueblo, said Tuesday. “The pueblos have joined forces in challenging the sales of pueblo cultural patrimony especially by auction houses in France.”

Heinrich plans to discuss the legislation Wednesday in Washington, D.C. The Democrat said his next step is to seek a Republican co-sponsor for the bill.