You don't and if Twitter does the same they wouldn't have to check either. Probably everybody operating a website is in violation of a law somehwere around the

You don't and if Twitter does the same they wouldn't have to check either. Probably everybody operating a website is in violation of a law somehwere around the globe. If you want to sell to European customers you will find that (depending on your size and business) you will have to comply with some laws in order to continue in this Market. The bigger your business the more rules and at a certain size laws will be created to regulate you in particular. This is what Twitter and friends face.