How much yardage is penalized for an illegal block after a valid or invalid fair catch signal?

An illegal block after a valid or invalid fair catch signal incurs a 15-yard penalty from the spot of the foul. This rule is in place to protect the player who has just signaled for a fair catch, ensuring their safety by penalizing any unfair play that disrupts their ability to receive the ball without being hit. The intention is to prevent players from being subjected to unnecessary contact immediately after they have indicated they are not looking to advance the ball. This penalty serves as a strong deterrent against actions that could lead to injury or unfair advantage during such critical moments of the game.