You can make some defensive arrangements like not supplying sources, or not transferring ownership for IP created until some trigger.
Another legal option is referring to international arbitration in your contracts (they can be enforced easily through borders of most of countries).
But realistically, even with basic contracts someone has ran away from you with sources means that the project was not that successful (because they will never be able to find serious investor having an open claim for their IP, even in another country).
So in best case everything will work, In worst - they will steal something what hardly worth stealing. The only real problem I can imagine in bad scenario is if it's your idea, they ran away and you are still bound by non-compete.