Be more Catholic than the Pope (himself) phrase
Usually used in a negative meaning to describe someone who is too religious or rule-following.
To adheres strictly to the rules, principles, and beliefs of the Catholic faith than is required by the church doctrine.
She criticized them for eating eat. I think she was more Catholic than the Pope himself.
To comply with any norm more stringently than is required by the dominant authority or normality standard.
Denmark is more Catholic than the Pope himself in terms of providing care for its citizens among the Nordic nations, which are all recognized for their outstanding social welfare programs.
To be dishonest or deceptive and no one can believe
No one believes what she said. She couldn't lie straight in bed.