Occasionally there have been televised interviews with reporters and border property owners that have demonstrated the ease of 'stepping across the border' into Mexico and then stepping back into the US. The reporter and the property owner then demonstrate that ease.
As I understand it (please correct if wrong) that is a violation of Title 9 Sec 1459 that requires immediate report of entry at a point that has not been authorized. (Assuming that the reporter and landowner failed to report to a customs inspection facility). The penalty for failure to comply is 5,000 dollars for the first violation.
Have the demonstrators just televised themselves committing the first stage of a US Customs crime?
(Note that I am using the term improper entry in it's generic meaning; a crossing at 'unauthorized location')