"This is not the first time that Mexican authorities have handed over an Arab from a country with known Al Qaeda connections to a local sheriff across the border. FBI picks them up and disappears"

This quote by John Culberson recommends that Mexican authorities have a history of turning over Arab individuals from nations with recognized Al Qaeda connections to local constables across the border. The implication is that the FBI then gets these individuals and takes them away, most likely for additional investigation. This suggests that the FBI understands the potential threat posed by people from countries with recognized Al Qaeda connections and is taking steps to make sure that they are kept an eye on and examined. This quote also implies that Mexican authorities want to work together with the FBI in order to guarantee the security of their residents and those of the United States.