A moral code is a set of principles that denote some human actions as ethically right and others as ethically wrong.
The "higher moral code" is the universal moral code that transcends time, culture, or situation.
For example, killing people for fun is ethically wrong, no matter what situation you are in, what culture you belong to, or what year it is. In that sense, the principle "no one should kill people for fun" belongs to the higher moral code.