Depends on the amount. It really depends what US STATE the man was in whether it does or not. For instance, anything 1k or up must be in writing in Georgia.

What you can do and what you should do are different things. If he's not keeping up his end of the contract, then sue him in the country the company is registered in. Don't give him time or the benefit of jurisdiction in any legal action. If you just don't like the guy, he likely still owns part of the business.