He offered no details on any new evidence, the Houston Chronicle reported Monday.
Ramos and another convicted former agent, Jose Compean, were freed Feb. 17, 2009, weeks after then-President George W. Bush commuted their sentences.
Ramos returned to El Paso for a few months, then moved with his family to the Houston area.
Both agents were convicted of shooting Osvaldo Aldrete Davila. Investigators said the agents never reported the shooting and tried to cover it up.
A jury found Ramos and Compean guilty of charges including assault with a dangerous weapon and discharging of a firearm in commission of a crime of violence. In October 2006, a judge sentenced Ramos to 11 years in prison and Compean to 12 years.
Former U.S. Attorney Johnny Sutton, who prosecuted the agents, defended the case, saying a jury convicted the two agents of serious crimes, and the case was "about the rule of law."
In 2008, Aldrete pleaded guilty to smuggling marijuana in separate incidents months after he was wounded. He was sentenced to more than nine years in prison.
