The usual rule in halachah, as far as business dealings, is הכל כמנהג המדינה - everything follows the local custom. This applies to things like expected product quality (Shulchan Aruch Choshen Mishpat 232:6), wages and benefits (ibid. 331:2 and 332:1), etc.
What about where the employer and the employees are in different locations with different practices, though? For example, if I live in the United States and own a factory in China, am I required to pay salaries comparable to those in the U.S., or do I go according to the prevailing rate there? What about things like health and safety regulations, child labor laws, and the like, which exist and are enforced in the U.S. (and thus fall under dina d'malchusa dina) but which in other countries may exist only on paper, if that?