International labor standards would have different effects on different groups of people. They would tend to help workers while harming consumers.
Workers would be helped by international labor standards. Workers in poorer countries would be protected more than they currently are. More protections for such workers might also mean that their firms would not be as able to undercut rich world workers on price. This might cause more jobs to return to/stay in rich countries, thus helping the workers in those countries.
Consumers, however, would be hurt. Companies would have to spend more to live up to the labor standards. This would end up raising the costs of the goods that those companies make. This cost increase would be passed on to consumers who would be hurt.
Thus, such standards would typically help workers while hurting consumers.