Can a bank that issued you a credit card take money out of your checking account to pay its past due balance if you are late 120 days?

Read the contract you signed when you applied for the card and I'll bet you find that provision is there. Bankers may like to get all the money they can, but they are VERY carefull to follow the law and the rules and regulations from FDIC or the state bank examiners. Little infractions cost them big fines when the examiners find them doing something wrong.