US attorney general Jeff Sessions may not be part of the biggest investigation in the Department of Justice, but as he reaches 100 days in office, there’s little doubt that he’s had an important impact on the American criminal-justice system—potentially for years to come.

Despite the political turmoil of the Trump administration, Sessions has moved to reverse a tide of progressive reform and to fulfill his boss’s law-and-order agenda, a collection of concepts loosely articulated during the 2016 presidential campaign. Sessions’ biggest actions, from undermining federal oversight of police departments to cracking down on undocumented immigrants, have worried a wide array of lawmakers, law-enforcement leaders, advocates and scientists.

“Of all the cabinet members, maybe even the president, he has to this point had the most significant impact as to policy changes,” said Jesselyn McCurdy, the deputy director at the American Civil Liberties Union (ACLU) Washington Legislative Office told Quartz.

Unlike his boss, Sessions is delivering on what he has promised—sometimes on causes he has championed for decades.

“There’s been a great bipartisan movement by organizations on the ground and members of Congress to reform the federal criminal-justice system, based on successes that have happened in the states, but the leader of opposition to that reform was Jeff Sessions, as a senator from Alabama,” McCurdy said. “These are all things that [Sessions], as a criminal justice reform opponent, had on his radar already.

McCurdy said Sessions was “definitely” living up to the ACLU’s concerns, and in some areas, fulfilling the worst-case scenarios.

Here’s a look at what Sessions has managed to do in just a few short months:

1. Created a false narrative

Starting from his very first comments as attorney general on Feb. 9, Sessions followed president Donald Trump’s lead by insisting that a bump in crime in the US is a “dangerous permanent trend that places the health and safety of the American people at risk.”

Violent crime is actually at near historic lows, and the increase in the last two years can be attributed largely to several big US cities. But Sessions is playing a long game here. Once the notion of national crime wave is established—or imagined—it will become the duty of the chief law-enforcement official to fight it. This sets the stage for a new war on crime, with the attorney general armed with misguided policies.

2. Boosted private prisons

Just two weeks after his swearing-in, Sessions took his first big step to dismantle the Obama legacy in the Justice Department, announcing he was rescinding an August 2016 memo from then-deputy attorney general Sally Yates to phase out the use of private prisons for federal inmates.

Yates cited concerns about their efficiency and safety. Sessions said Yates’ decision impaired the DOJ prison agency’s “ability to meet the future needs of the federal correctional system,” hinting at impending plans that will likely swell the federal prison population: the Trump administration’s immigration crackdown and Sessions’ own revived “War on Drugs.”

While private prison companies’ fortunes have been soaring since Trump’s election, it’s important not to overstate Sessions’ decisions on the federal level in the context of mass incarceration. The federal system holds only 13% of the country’s inmates, and only about 18% of them are in private facilities. Still, these policies will affect tens of thousands of people.

3. Re-instituted the War on Drugs

In keeping with his reputation as anti-drug crusader, Sessions started his renewed campaign with a speech in which he called marijuana “only slightly less awful” than heroin. With rising support for marijuana legalization, Sessions’ harsh stance is an unpopular one—something that he acknowledged, saying that his belief is “unfashionable.” But his isolation hasn’t stopped him from putting his words into action.

On May 12, he sent a memo to federal prosecutors around the country, instructing them to pursue the most serious penalty possible for any given offense. In practice, this includes charging nonviolent, low-level drug offenders with long mandatory minimum sentences, a practice reminiscent of the 1980s and ’90s War on Drugs. This also was a reversal of an Obama-era policy, introduced by then-attorney general Eric Holder. Commenting on Sessions’ decision, Holder called it “dumb” and ideologically motivated. Again, this pertains only to a relatively small number of overall US offenders, but it represents an important symbolic shift. “This is the worst thing he could’ve done,” McCurdy said.

4. Faithfully executed Trump’s immigration policies

Sessions can’t build Trump’s border wall, but he sure can make good on the president’s other anti-immigrant promises. In April, Sessions, at the US-Mexico border, announced: “This is the Trump era.” He explained what that meant: instructing prosecutors to charge immigrants re-entering the country with a felony rather than a misdemeanor and telling them to crack down on the “harboring” undocumented immigrants.

He also announced that he would be sending more immigration judges to states on the Mexican border through a new “streamlined” hiring plan. Speaking about drug cartels that “turn cities and suburbs into war zones,” Sessions said that “it is here, on this sliver of land, where we first take our stand against this filth.”

5. Let police off the hook

Supported by the country’s largest police union, Sessions and Trump have talked up their support for law-enforcement officers. Even in his immigration memo, the attorney general says that his most important instruction to prosecutors is to make pursuing crimes against federal law-enforcement agents a top priority.

Just days earlier, the DOJ announced a wide review of agreements with police departments across the country, potentially undermining important reforms across the country. These so-called “consent-decrees,” first introduced in the 1990s and ramped up during the Obama administration, have had undoubtedly mixed results. Advocates emphasize their importance for keeping police accountable. No one can say this was a surprise—Sessions opposed consent decrees when he served as US senator, and during his confirmation hearing for attorney general he said they “undermine the respect for police officers.”

6. Downplayed the importance of science in the courtroom

In yet another reversal from the previous administration, the DOJ under Sessions will not go out of its way to advance and promote reliable science in the courtroom, despite pleas from the country’s top criminologists and forensic scientists. Sessions did not renew the term of the National Commission on Forensic Science, a body formed in 2013 to study methods used to gather and assess evidence in US crime labs, some of which had been discredited as scientifically unsound. Instead, forensic science will now fall under the purview of an internal task force—a move experts warned against. The DOJ also suspended a review of testimony by FBI experts, who have been giving misleading accounts about evidence in court for years.