As US officials use new sentencing guidelines to release drug offenders from federal prison in an effort to reduce the country's massive inmate population, they are taking an opposite approach to the undocumented population: pushing to increase federal prison time for crossing the border.

The US Sentencing Commission (USSC) has proposed to increase sentences for immigrants who illegally re-enter the country after being deported. The cases are a hefty part of the criminal justice system, according to the commission's data, making up a quarter of federal sentencings each year.

The proposed amendment, which the commission is due to vote on this Friday, would raise base sentences for illegal reentry with no other criminal offenses from between zero and six months to between six and 12 months in federal prison. The maximum penalty for the crime — two years — would remain the same, but could theoretically be extended as high 20 years depending on the offender's criminal history.

The Department of Justice has voiced adamant support of the amendment. Michelle Morales, the DOJ's acting director of policy and legislation, submitted comments to the USSC on behalf of the department last month, saying in part, "The Department agrees with the Commission that defendants who are convicted of illegal reentry offenses on multiple prior occasions should receive enhanced punishment, and believes that such offenders should receive enhanced punishment regardless of any other criminal history they may have amassed."

The DOJ noted that 27.2 percent of illegal reentry cases involve individuals who had already been convicted of illegally entering the US, and stated that more needs to be done to deter unauthorized border crossers.

"The need for additional punishment for persistent immigration offenders is plainly evident, and the Department applauds the Commission's action to address this problem," it said.

A spokesperson for Immigration and Customs Enforcement did not respond to requests for comment on the detention of migrants for illegal reentry or on the proposed USSC amendment. A USSC spokesperson emphasized that the commission had not yet issued a final vote on the proposal.

'There isn't any evidence we've seen that shows this works.'

Immigration advocates argue that harsh reentry penalties have the effect of overburdening prisons and federal courts rather than discouraging illegal border crossings. The commission's amendment would establish suggested sentences rather than mandatory ones, but federal judges issued more than half of their sentences within the guidelines in 2014, according to the most recent USSC data.

"These are recommendations for judges to follow — they're not mandatory, but they're a very important tool. This is an influential document," said Joshua Breisblatt, a policy analyst with the American Immigration Council.

Harsh illegal reentry convictions have already strained the criminal justice system. According to the Pew Research Center, the cases have been the number one cause of federal prison growth over the past decade. The number of people sentenced in federal court more than doubled between 1992 and 2012, from 36,564 to 75,867 — and the boom in illegal reentry sentences made up 48 percent of that increase. People were once typically deported for illegal reentry, but the most recent USSC data shows that offenders now serve an average of 17 months in prison before their removal from the country.

"You're spending all this money and time filling up prisons, and for what?" Breisblatt asked. "US Customs and Border Protection sees this as part of a consequence delivery system — that there should be some type of consequence beyond being sent back if you cross the border.... But there isn't any evidence we've seen that shows this works. It's unclear what effect it's having when you could be putting them through normal removal proceedings without clogging up the prison system."

Grace Meng, a researcher with Human Rights Watch, agreed that criminal penalties have not deterred undocumented immigrants from repeatedly trying to enter the US. While researching illegal reentry for a 2013 HRW report on border prosecutions, she interviewed dozens of migrants who told her that the prospect of prison sentences did not discourage them.

One of them, a Mexican woman identified in the report by the pseudonym "Alicia," tried to enter the country multiple times after her first deportation because she wanted to be reunited with her two US-born daughters, one of whom had a failing kidney.

"I have not lost the desire to try again," Alicia told Meng as she journeyed north through Mexico after three prior deportations, including two stays in detention.

Many others recounted similar stories.

"Our immigration system hasn't allowed many families to stay together," Meng said. "There are strong humanitarian reasons people have for wanting to be here.... Their motives are not in any way comparable with someone who wants to commit a crime."

With no evidence that prison time has served as a deterrent to future crossings, Chris Rickerd, policy counsel for the ACLU, said that the commission's amendment seemed arbitrary and potentially damaging.

"It's a huge concern for us that there was no justification to increase sentences at the low end of the scale," he said. "It doesn't fit into the administration's national security framework to sweep up people coming here for their family or for work."

Though their only crime is entering the country, undocumented immigrants get sent to some of the worst prisons in the nation called CAR (criminal alien requirement) facilities, Rickerd said. Because the facilities only hold non-citizens who will be deported after their sentences, the federal government does not require the private prison companies that run them to offer social services available in other US prisons.

"Many people who are detained in these facilities are totally unfamiliar with the criminal justice system," Rickerd pointed out. "These facilities are literally warehouses, not geared towards reintegration into society."

As officials debate whether to lock up repeat border crossers for longer stays, advocates are urging a less punitive approach.

"We have a broken immigration system that hasn't allowed families to stay together," Meng said. "The commission should not be trying to increase punishments more for people trying to reunite with their families."