What country is GMO illegal in?

Could you please provide some clarification on the matter of genetically modified organisms (GMOs)? Specifically, I'm curious to know which countries have outlawed the use of GMOs. Could you enumerate some of these nations and perhaps provide a brief overview of the reasons behind their bans? Additionally, are there any international treaties or agreements that prohibit the use of GMOs globally, or is it primarily a country-by-country decision? Thank you for your assistance in answering this question.