He also pointed out that many immigrants in the federal system may simply be there because they lack legal immigration status -- not for having committed flagrant criminal offenses.
"No community is immune from the ravages of drugs and sexual violence. But the overwhelming majority of those crimes are not done by immigrants," Johnson said. "We don't ask criminals about their political affiliation or their religion. So why should we focus on their immigration status?"
Immigrations and Customs Enforcement officials say they continue to prosecute crimes committed by immigrants, including cases of sex trafficking. The agency investigated 557 sex trafficking cases between 2005 and 2007 and convicted 129 offenders, according to the most recent data.
Sex trafficking, or the recruitment, transportation and use of another person for the purpose of trading sex for money, has become an alarming trend in recent years.
An estimated 240,000 American children are at risk of commercial sexual exploitation with the average age of first-time prostitutes ranging from 12 to 14, according to a recent Justice Department study.
Laguna-Guerrero, who allegedly began trafficking his girlfriend when she was 16, currently faces a trial in U.S. Federal District Court. If convicted, he faces up to life in prison.
ABC News' Julie Percha contributed to this report.