CBP officers found the male member of the family was a registered sex offender and was also convicted of second degree sexual assault.
The offender was convicted for sexual conduct with a person under 13-years-old in 2001.
Authorities sent the teenager home to his caregiver.
New Zealand Police said they were aware of the incident and enquiries were ongoing.
"CBP follows strict federal standards in the protection and well-being of minors traveling alone," said Carlos C. Martel, CBP Director of Field Operations in Los Angeles.
"Minors are particularly vulnerable to sexual predators that commonly present themselves as individuals they can trust.
"CBP officers took decisive action to protect a potential victim from a convicted criminal."
