Usage patterns
〈事〉の儀を執り行うto conduct/hold the ceremony of ~
They conduct the wedding ceremony.
〈事〉の儀に付きregarding the matter of ~ (formal)
Regarding the matter of my retirement, I am writing to inform you.
〈人〉儀as for [person] (formal suffix used in official notices)
As for Tanaka Taro, he will be retiring this time.
Expressions
その儀that matter; those matters 余の儀another method; another problem