this is a strawman argument; i've never heard anybody push the idea of banning components that are produced at too low of a wage.
but, mexico's low wages are not an accident. they can't unionize. the cops are thugs. these are issues that the government has to address. in a word, the problem in mexico is corruption.
would you would do, then, is introduce punitive tariffs in regions that do not apply appropriate labour standards (including collective bargaining rights and proper wage floors), as well as environmental standards. there's no banning involved. there's just pricing out
..and, if that leads to labour unrest, that's a good thing.
i'm not naive: i understand that none of these governments represents the interests of workers. what mexico really needs is a way to kickstart it's labour movement, which is currently bogged down by government regulations. if i wanted to be snide, i could say something about cutting the red tape around the rights to organize and strike.
what a nafta deal can do is actually minimal - it can lay a law of decent standards down, and exclude them through tariffs if they won't comply. it's mexican workers that then need to rise up and demand their rights. and, if you think that sounds like colonialism, you can type me up an essay explaining your viewpoint from a cushy seat in the ministry of labour rights.
again: we're not going to get a lot out of this from the top down, and we should all be aware of that. but, there is some possibility that all of this unrest is leading capital to the realization that it needs to do something about the unemployment levels that nafta has left us with. forcing mexico to acknowledge collective bargaining rights is actually a pretty basic requirement. it's easy to say that the deal shouldn't have gone through without it, except that it was actually the point, and we can see that this was a mistake (we have increasing levels of unrest, not tech jobs for all). this is in truth very much long overdue, entirely feasible and entirely attainable - and all decent people should support it.
https://www.nytimes.com/2017/08/22/business/economy/nafta-labor-unions-wages.html