...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 is different.
I don't know. I feel I'd let her through, but...
...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.