Generally, you have the right "choice of laws" in a contract, and it is usually enforceable. IOW, you can say "This contract shall be construed and enforced in accordance with Shari'a as interpreted by the Ayatollah Ruhollah Khomeini," and that's the law will generally be enforced. The glaring exception is where (as some jurisdiction hold with respect to some elements of noncompetes) part of the agreement is unenforceable as a matter of policy -- i.e. "We don't do that here."
I suggest that you consider the following: Figure out what jurisdiction (yours or theirs) has the law which best favors you, and choose that law and include language that jurisdiction shall lie only in the courts of that state, which is another thing you can choose, so long as there is some connection between the agreement or parties and the chosen state.
I would go "belt and suspenders" and add a paragraph saying that the idea/process/whatever-i- is is acknowledged to be the property of [YOU] and that [HE] agrees that you are entitled to all revenues from the use or exploitation of whatever-it-is by either of you or by any person to who the whatever-it-is may be transmitted.