A few weeks after Suffolk District Attorney Rachael Rollins pushed Massachusetts lawmakers to back safe injection sites following a Philadelphia federal judge’s ruling that they do not violate federal drug law, Sen. Elizabeth Warren told Rollins that the sites could be effective in combating substance abuse.

The Boston Herald reported that Warren, during the Second Step Presidential Justice Forum at Benedict College in South Carolina on Sunday, told Rollins that safe injection sites “talk about both saving lives, but also opening the door for people who say, you know, ‘Maybe now’s the moment I could try. I could try rehab.’ I believe in that. In a Warren administration, we’re going to follow the data on this.”

In August, Warren released a criminal justice plan in which she said mass incarceration has not reduced addiction rates or overdose deaths, “because substance abuse disorder is a public health problem, and it’s long past time to treat it that way.” She called for greater investment in diversion programs, treatment programs and “evidence-based” safe injection sites and needle exchanges.

Warren and her Democratic rivals Sen. Bernie Sanders of Vermont, Sen. Cory Booker of New Jersey, businessman Andrew Yang and former U.S. Rep. Beto O’Rourke of Texas have expressed support for safe injection sites. The Department of Justice under President Donald Trump has pushed to block the sites, prosecuting based on the so-called “crack house statute” barring anyone from managing a building where illegal drugs are used.

Presidential candidate and former Vice President Joe Biden co-sponsored the statute when he was a Delaware senator in the 1980s. While Biden has admitted some mistakes regarding previous criminal justice laws he backed, he has not shared a firm position on safe injection sites, Philadelphia Magazine reported.

The Sunday exchange between Warren and Rollins follows Rollins’ Oct. 8 letter to Massachusetts lawmakers expressing strong support for legislation that would establish safe injection sites and enable health care professionals to assist those with substance abuse disorder to safely consume drugs.

Rollins described the ruling as an “historic turning point” that affirmed the facilities’ legality under federal law. She said addiction presents major public safety concerns in the Greater Boston region, and said the opioid crisis “does not discriminate based on race, wealth, age or orientation. Everyone is impacted.”

A state commission tasked with studying ways to reduce harm from the epidemic recommended piloting one or more sites, which Canada and some European countries already use to combat addiction. Supporters say the sites would be particularly valuable as the potent synthetic opioid fentanyl grows more common in overdose cases.

Rollins’ letter put her at odds with U.S. Attorney Andrew Lelling, who said he respectfully disagrees with Judge Gerald McHugh, the federal judge who earlier this month ruled that a nonprofit’s plans to open a supervised consumption site in Philadelphia would not violate federal law. Lelling said any efforts to open such a facility in Massachusetts “will be met with federal enforcement.”

While some lawmakers and municipal leaders in Massachusetts have expressed support, Gov. Charlie Baker told WGBH earlier this year that there was no data to support safe injection sites in the commonwealth. Baker also cited a “strongly worded op-ed” by Lelling in the Boston Globe noting anyone would be arrested if they tried to open a site.

The ruling in Philadelphia won’t be the last word on the matter, with likely court appeals and future prosecutions in other cities and states. The U.S. Justice Department said after the ruling that “any attempt to open illicit drug injection sites in other jurisdictions while this case is pending will continue to be met with immediate action.”