According to arnold and bowie, are mnes responsible for the practices of their subcontractors and suppliers?

They are definitely responsible.

Explanation:

Denis Arnold and Norman Bowie advocate for corporate responsibility in their article "Sweatshops and Respect for Persons" (Business Ethics Quarterly 13 - 2003).

"MNE's have a moral duty to ensure their business partners respect employees by ensuring that human rights are not violated in the workplace."

Corporations can't turn a blind eye on abuses committed in countries where they outsource their production.