Where can I find denied boarding regulations? What legislation protects air passenger rights? How are protected flight rights EU?

Regulation (EC) No. 261/2004 regulates the payment for overbooked flights, also it describes the overbooked flight rights of air passengers and responsibilities of airlines. The rules of compensation and contribution to passengers in events of delayed, canceled and denied boarding flights are indicated in this law. You will find more information in Air Passenger Rights.