If he decides to do business in the states, he becomes liable for his business dealings, but only as a partner. Should creditors catch wind of the fact that the business is under his name, they may try to bring suit against him by stating that the business that he is running here is essentially him but in a company veneer (this is called piercing the corporate veil
Some of the ways to avoid that is to have a small percentage of the company and not a controlling interest, not use your own name on checks, business stationary, or business records.
If clients pay for import goods, partner names may appear on the import goods, but it all depends on how the foreign partnership is set-up. Here, it is based on international law of the country where the business is set-up, and not US law.
Creditors, if they go looking, may be able to find him if he uses his social security number (or alien registration number) in conjunction with the business, or if he advertises.
Hope I was able to answer your question. Good luck!
Dimitry Alexander Kaplun, Esq.