I guess I'm not expressing myself well.
1. Yes European countries (of the EC) have laws requiring that you carry an ID card with you. If you are anywhere in the EC with your national ID card, it demonstrates you are here legally. So, if I go to Spain with a national ID card from France or Germany and am asked by LEOs to show it, it demonstrates I'm in the country legally. It applies to all the EC. If you don't have an ID card, either you are in this country illegally or you are breaking the law going to a country without your national ID (or passport for that matter. You can see a national ID card as a small more convenient passport that demonstrates citizenship). If you immigrate to Europe from a non EC country you're supposed to carry proof of being there legally.
2. If you are asked by LEO for a national ID card then it shows you are a citizen. If you are not then you are still required to show your Visa or I94 and passport or green card. If you can't show any of this it goes back to the previous point: you are either here illegally or are breaking the law by not carrying your information showing you are here legally eg green card etc.
1. Yes European countries (of the EC) have laws requiring that you carry an ID card with you. If you are anywhere in the EC with your national ID card, it demonstrates you are here legally. So, if I go to Spain with a national ID card from France or Germany and am asked by LEOs to show it, it demonstrates I'm in the country legally. It applies to all the EC. If you don't have an ID card, either you are in this country illegally or you are breaking the law going to a country without your national ID (or passport for that matter. You can see a national ID card as a small more convenient passport that demonstrates citizenship). If you immigrate to Europe from a non EC country you're supposed to carry proof of being there legally.
2. If you are asked by LEO for a national ID card then it shows you are a citizen. If you are not then you are still required to show your Visa or I94 and passport or green card. If you can't show any of this it goes back to the previous point: you are either here illegally or are breaking the law by not carrying your information showing you are here legally eg green card etc.