strict; inflexible; stickler for the rules
Describes a person or attitude that rigidly adheres to rules without flexibility. Often used critically. The literal image is of measuring everything with a ladle (杓子) as if it were a ruler (定規).
彼は杓子定規な人で、例外を認めない。
He is a stickler for the rules and doesn't allow exceptions.
Applying rules inflexibly can sometimes cause more problems.