According to an affidavit, both men are accused of lying to cover up their efforts to support terrorism. The arrests are now renewing a debate over bringing refugees from Syria and other countries to the U.S., reports CBS News correspondent Jeff Pegues.
Court documents allege that Omar Faraj Saeed Al Hardan and Aws Mohammed Younis Al-Jayab - both Palestinian-born Iraqi refugees -- were intent on fighting alongside terrorist organizations in Syria.
Al Hardan had been in the U.S. since around November of 2009, while Al-Jayab arrived in October of 2012.
According to court documents, 23-year-old Al-Jayab used social media to communicate with people inside Syria in 2012, expressing a desire to return to Syria to "work."
He was also allegedly communicating with 24-year-old Al Hardan, who prosecutors say is associated with members and sympathizers of ISIS.
While living in Arizona and Wisconsin, Al-Jayab spent time at a gun range, pleaded for travel funds and asked online friends for guidance on how to reach Syria, according to court documents.
By March of 2013, Al-Jayab had a strategy, saying "I am coming to Syria... I have planned a route and everything," then in April saying, "I am eager to see blood."
After receiving a $4,500 insurance settlement in November of 2013, Al-Jayab flew from Chicago to Turkey and then made his way to Aleppo, Syria.
But he was wise to American surveillance tactics, telling one associate online, "the government is alert for everything... my trip constitutes a charge."
He returned to the U.S. in January of 2014. Investigators say Al-Jayab lied in customs forms and multiple interviews months later, telling immigration officials he went to Turkey to visit his grandmother.
The charges provided political blow back aimed at the White House. Texas Gov. Greg Abbott said in a statement: "This is precisely why I called for a halt to refugees entering the U.S. from countries substantially controlled by terrorists."
The U.S. attorney in California's eastern district said there's no indication Al-Jayab "planned any acts of terrorism" in the United States.