El Duque 2,

Anyone turned away at the border is automatically put on their "list". The next time you attempt to cross, you will be "interview" for suitability etc. Each and every time. If you are connecting and just transiting through the states in an airport, you will be delayed and flagged and you will miss your flight.

There are different categories they place you in. In the lowest category, your name is on the list for a minimum of 75 years. All categories above that, your name is in the system in perpetuity.

The customs officer have broad powers to deny your entry. There is no avenue of appeal.

If you look at the guy the wrong way, he can deny you.

If you are facing a politically motivated CBO, you are hooped.