SAN DIEGO -- A San Diego student who discovered he was on a U.S. government no-fly list when he tried to fly home from Costa Rica, walked across the border at San Ysidro Thursday evening into the arms of his family.

Self-described peace activist Kevin Iraniha, 27, was prevented from flying home with his family after his law school graduation. A graduate of San Diego State, Iraniha just completed a master's degree program in international law at University of Peace in Costa Rica.

Iraniha, who grew up in San Diego, had no problems when he flew from Costa Rica to San Diego to spend the holidays with his family.  But when he tried to board his flight home on Tuesday, airport officials pulled him from the line. He was questioned by FBI agents attheU.S. Embassy for three hours. No one would tell him why he had been placed on the no-fly list.

"[I was] asked about when I traveled, where I stayed, for how long," Iraniha told Fox 5. "It seemed like they were trying to figure out why I was on the list as well."

Last summer, Iraniha said he traveled to Iran to visit his grandparents and to Egypt to observe the Arab Spring protests.  But he denied doing anything to warrant being on a no-fly list. 

Embassy officials told him he couldn't fly to the US but he could cross the border on foot. So Thursday, he flew from Costa Rica to Mexico City, where he caught a connecting flight to Tijuana. Late that afternoon, he walked across the border to San Ysidro.

"You see my bloodshot eyes. I'm still going through it," Iraniha said. "It's very tiring and it was very depressing."

Iraniha's family is bewildered by the government's treatment of their son.

"Why they put him on this no-fly list … none of this makes sense," his father said. "Whoever did this is not American."