I recall an example of when a Mexican worker in an LG plant lost her hands in a poorly-maintained stamping press. Theoretically Mexico has robust worker protection laws, but in reality the courts are corrupt and controlled by the maquiladoras.
So instead lawyers tried to sue LG in US court on her behalf. In fact they sued the actual TVs being imported by LG US that were made in her factory, the same way counterfeit goods are sued and arrested at the border by intellectual property owners.
The US judge dismissed the case arguing that the TVs were owned by LG US, who bought them in Mexico from LG Mexico. Both companies being owned by the same parent company is irrelevant to the law which saw them as completely separate entities and neither LG US nor the TVs it bought have any responsibility for the conditions in the Mexican factory.
Now if the drafters of NAFTA cared at all about worker conditions they could have easily made liability follow the goods across the border the same way they made copyrights and trademarks follow the goods across the border. They did not care about the workers and in fact they saw the mistreatment of workers as an advantage of the free trade deal.