Hudgens, 27, and Butler carved their names in a heart into a rock formation in Sedona, Arizona over Valentine's Day weekend and might have broken a federal law, reported ET online.
According to a public affairs officer for Coconino National Forest, the incident involving Hudgens and Butler, 24, "is under investigation."
"Officials at the Coconino National Forest became aware of the incident (Monday) when the media alerted them of the situation. There is no deadline for this investigation -- it takes as long as it takes. The maximum punishment for this is USD 5k and/or 6 months behind bars."