President Trump was "eager" to sign the bipartisan First Step Act into law on Dec. 21, 2018. During his 2019 State of the Union address, Trump touted the new law's success.

“This legislation reformed sentencing laws that have wrongly and disproportionately harmed the African-American community,” Trump explained on Feb. 5. “The First Step Act gives nonviolent offenders the chance to reenter society as productive, law-abiding citizens. Now, states across the country are following our lead. America is a nation that believes in redemption.”

WHY ARE WOMEN WEARING WHITE TO THE STATE OF THE UNION? DEMOCRATIC LAWMAKERS AIM TO SEND 'LOUD AND CLEAR' MESSAGE

The First Step Act – or the Formerly Incarcerated Reenter Society Transformed Safely Transitioning Every Person Act – is, at its core, a directive for the Justice Department to establish a system to assess the risk of a person to re-offend as well as to create housing or other incentives for offenders to participate in recidivism reduction programs.

The bill, which passed the Senate 87-12, culminates years of negotiations and GAVE the Trump administration a signature policy victory. It’s been heralded by conservatives and liberals, celebrities and Jared Kushner, the president’s son-in-law, who worked the halls of Congress for months to forge a compromise.

Sen. Cory Booker, D-N.J., heralded the bill as a start to righting the country’s “broken” criminal justice system.

“But for the first time in a long time, with the passage of this bill into law, our country will make a meaningful break from the decades of failed policies that led to mass incarceration, which has cost taxpayers billions of dollars, drained our economy, compromised public safety, hurt our children and disproportionately harmed communities of color while devaluing the very idea of justice in America,” Booker, a potential 2020 presidential contender, said.

The law affects only federal prisoners, who make up less than 10 percent of the country’s prison population.

Read on for a look at what the new law changes.

Change life sentences

In an attempt to focus the harshest sentences on the most violent offenders, the law lowers the mandatory minimum sentences for prior drug felonies. Drug offenders with three convictions – or “three strikes” – could face 25 years in prison instead of life.

More discretion for judges

Federal judges will be given more leeway for their discretion when sentencing certain drug offenders.

Rehabilitation efforts

The law allows some 2,600 people serving sentences for crack cocaine offense before August 2010 the opportunity to petition a judge for a reduced penalty.

It also incentivizes prisoners to participate in programs designed to reduce the risk of recidivism, with the reward being an earlier release to either home confinement or a halfway house to complete the sentence. Recidivism programs can come from nonprofits, faith-based organizations, institutions of higher education and private entities.

This option will not be made available to offenders who were also convicted of violent firearms offenses, sexual exploitation of children or high-level heroin and fentanyl dealing.

Credit for good behavior

Prisoners could get seven days of credit for good behavior each year of his or her sentence with this law – with the credits being deducted from the sentence to allow for early release.

For example, an inmate serving a 10-year sentence who earns the maximum credits each year could be released 70 days early. This change could save $414 million in the next 10 years, according to the Congressional Budget Office.

Additionally, the law expands eligibility for elderly or terminally ill prisoners to secure compassionate release.

Reaffirming existing rules

The law also addresses existing laws and regulations, seeking to reaffirm enforcement of those, according to The Marshall Project.

For example, it expressly prohibits the use of restraints on women who are pregnant, in labor or in postpartum recovery. This has been prohibited since 2008.

Additionally, it would require officials to place imprison offenders no more than 500 driving miles away from their home or family, according to The Marshall Project.

Fox News' Samuel Chamberlain and The Associated Press contributed to this report.