Throughout history, the Church and the Pope have used different methods in order to achieve their goals. One of them is the interdict.
Interdicts where a ban on people over certain religious rituals. So, the pope could use this threat in two main ways: to prevent and to punish.
Back in the day being interdected was a social status that put shame and social pressure upon the person or the people afflicted, so for example if the pope wanted to achieve a certain goal, he could threat whoever was in the middle of his way to interdect him/her/them.
As for the punishment, being interdect was a sufficient punishment for many people, after they had rebelled, or in some way disrespect the authority of the pope.