Running a contest (almost) internationally?

Does anyone have any experience with running a contest internationally, or very close to it? I want to create a contest where everyone who makes a purchase with my site can submit their slogan or logo or something of the sort. Each submission would then be posted, and a winner would be picked.

a) MOST IMPORTANT- legal issues/guidance... should I contact a lawyer? They are only able to give me advice about my country but I would like to allow submissions from as many countries as possible.

b) Anyone know of a readymade platform that can handle this? If not I guess I could hire a freelancer to make it.

Thanks for the help blackhatters

No ideas anyone?

I really need help!! BUMP

I want to find out as well but I think you must play it safe and contact your lawyer for more info.