We've got environmental laws that keep people from damaging the environment by dumping nasty chemicals into either the ground or the air. These laws make it more expensive to make stuff, since it so happens that typically the cheapest way to do something is usually the most noxious. (Probably because costs are circumvented by dumping loose which turns them into externalities.)
So, if you want to make a TV set or a computer, you have to keep things clean and spend money to filter out and neutralize what would otherwise become pollution.
However it's perfectly okay to make the TV set or computer in a place that allows the pollution and then import it to here and sell it like it's no different.
That seems to completely defeat the spirit of making the environmental laws in the first place since it's all the same air and water anyway--it solves the issue of pollution as much as transferring the mess from your room into your sibling's room solves having to keep your room clean. In fact, although it's technically valid, it's completely insincere in spirit in exactly the same way as some religious people use automatic elevators and appliances to circumvent the inconveniences in their religions.
If we're going to have environmental laws, it seems they should be comprehensive enough so that when something is imported, there should be a fee to compensate for whatever gap in environmental standards there is wherever it came from. Otherwise, we're not making anything cleaner or solving any problems, we're just shuffling the pollution out of sight.
A possible criticism might be that the argument could be extended to everything that could be different in other countries. For example, saying that if we have such a thing as minimum wage here, likewise all imports should be adjusted to compensate for places with lower standards and wages. However I don't think this applies to more than the environmental aspect because it's the same, single environment everywhere, whereas things like workforces in other countries are separate and distinct.