Why is that person a problem? That is why rule of law exists, ideally, so that we don't run society on arbitrary outraged moral judgement. E.g. many people are morally outraged by presence of any illegal immigrants and others are outraged by any enforcement against undocumented immigrants. If we base decisions on arbitrary outraged moral judgement it's not going to go well.
A "loophole" is only a "loophole" to someone who agrees with yours. And I say it as someone who agrees in this particular instance.
That person is a problem because low-trust environments are inherently low-privacy and low-efficiency environments. Allowing a small portion of the population to destroy trust and then justifying it with "well there was no explicit rule against it" is parasitic on the whole society. It's better to stand up and say "this is unacceptable and clearly not what was asked for".
That is only as far as you or I are concerned. The environment where you first write the rules then someone can arbitrarily come and say nah that's not what we meant (with any consequences) is far worse than any low trust environment. Vague rules with selective/interpretative enforcement is in fact what authoritarian countries like Russia/China tend to use. Disturbing social harmony is illegal and all the right thinking people know it when they see it.
A "loophole" is only a "loophole" to someone who agrees with yours. And I say it as someone who agrees in this particular instance.