I am working on a videogame which involves recognising flags, emblems and insignias. I've been getting public domain images from Wikipedia. I don't know much about the laws surrounding flags etc but I've noticed some of the flag images are accompanied by the text "This image shows a flag, a coat of arms, a seal or some other official insignia. The use of such symbols is restricted in many countries. These restrictions are independent of the copyright status."
I was wondering if anyone here knew much about these kinds of restrictions and whether they might apply to my situation (or whether you could point me towards any resources on this which could be useful).
Commons:Non-copyright restrictions is the Commons guideline. I don't know much about them either, and they encompass many different things, but I think it's mostly common sense such as not breaking your country's law by using it (also considering that certain symbols are illegal in some countries), or not using an organization's logo to falsely claim affiliation with it.