It's my experience that once you get sent to secondary they have already decided to fuck you, they are just deciding which flimsy excuse they will use to do it. My totally non-legal conjecture (and livid experience) is if you are a citizen they will play mind games with you in secondary or a holding cell for hours to a day or so and then eventually reluctantly release you after muttering threats about revoking your passport and/or not letting you in.