I believe you're correct. When foreign experts visit temporarily to transfer technology to a new site, there's no bright line between the "non-working" business

I believe you're correct. When foreign experts visit temporarily to transfer technology to a new site, there's no bright line between the "non-working" business activities permitted by a B visa or ESTA and those requiring H or L visas. If the DHS thought Hyundai had pushed that line too far, then they could have subpoenaed their records, and perhaps ultimately settled the case with a fine and a promise to comply with the clarified standard in future. That would all have been normal. They instead chose to lock up random employees "working" in a way their employer had probably assured them (rightly or wrongly) was lawful. That's not normal. The USA is a sovereign country, so it can impose whatever immigration policy it wants. No one should be surprised when foreign multinationals adjust their investment decisions accordingly though, or when American staff abroad face reciprocally unpleasant treatment.