This is the 7948th most frequent Russian word.
кодексом
"Кодексом" means "by/with the code" or "under the code" in English (instrumental case of "кодекс," meaning "code" or "codex").
The word 'кодексом' is used here in an instrumental case to indicate adherence to a set of rules or guidelines.
Он поступил согласно кодексом чести.
He acted according to the code of honor.
Here, 'кодексом' indicates a compilation of laws as a guiding principle, using the instrumental case.
Мы руководствуемся кодексом законов нашей страны.
We are guided by the code of laws of our country.
In this sentence, 'кодексом' is instrumental and refers to a specific set of behavioral regulations.