The USA for example has a law which requires an alien to carry immigration documents / ID on their person at all times. When flouted it is a misdemeanor and punishable by up to 30 days imprisonment.
Every alien, eighteen years of age and over, shall at all times carry with him and have in his personal possession any certificate of alien registration or alien registration receipt card issued to him pursuant to subsection (d). Any alien who fails to comply with the provisions of this subsection shall be guilty of a misdemeanor and shall upon conviction for each offense be fined not to exceed $100 or be imprisoned not more than thirty days, or both.
In the UK apparently this requirement does not exist however does my credit/debit card with my name suffice as ID (not for driving, just for example if a ticket officer wants to check my ID on the metro) in cases where an ID may be required in the UK?