Большой англо-русский и русско-английский словарь
as obliges, as requires, out of smth. по долгу службы ≈ in one's official capacity, in the performance of one's duty по долгу чести ≈ true to one's honour
по долгу в энциклопедиях
as obliges, as requires, out of smth. по долгу службы ≈ in one's official capacity, in the performance of one's duty по долгу чести ≈ true to one's honour