If application and enforcement correlates with nationality because those violating the law are more likely to be of a given nationality, then I don’t think that

If application and enforcement correlates with nationality because those violating the law are more likely to be of a given nationality, then I don’t think that is a problem. But I think enforcing the law to a different degree against similar violations of distant nationalities wouldn’t be fair. That is, if 10 Canadians and 10 Mexicans crossed into the US illegally, and all faced similar consequences, I think that’s fine. If there are only 1 Canadian and 10 Mexican violators and this causes limited border patrols to be distributed proportionally between the US-Canada and US-Mexico border, I think that’s still fine. But if 10 violating Canadians and 10 violating Mexicans who were all apprehended faced different consequences, that would not be fair.