Choosing between having enough money for medicine for my son, or letting a woman with incorrect documents come through (her husbands were OK, and she was claiming that she would be murdered on deportation) was fairly harrowing.
This game is an excellent illustration of what allows evil to happen.
I denied her entry even though I didn't have any citations. Rules are rules. Her husband will have to think about how he thought he could tug on my heart strings by going through first when he knew his wife's papers weren't in order.
...it makes game-theoretic sense not to let that person pass. Even not counting the fact they already tried to trick you into doing what they want you to (by husband going first), you have no guarantee that she's telling you the truth. And as soon as you let her through, you can expect dozens of people trying to play the same trick on you.
Laws need to be upheld more-less consistently, otherwise they don't work at all. An inconsistently enforced border check doesn't eliminate the "going through with invalid papers" from the solution search space for people.
This game is an excellent illustration of what allows evil to happen.