“You have to realise, Jean Morbern was horrified when he realised what … what godlike things he had done. Creating the timestreams meant creating millions, billions more people, all individuals, all with rights. He didn’t mean to create the streams — they just … happened when he made his first visits upstream, before he’d got the hang of probability shielding. He felt he had no right to create them and therefore no right to uncreate either.”

Morbern’s Code was devised to govern the way in which the College operates, to safeguard the rights of bygoners and in general to ensure that things happen in a way of which Morbern and his Creator would approve.

Only a couple of passages of the code are actually cited in Time’s Chariot:

“I will deny to no one to whom the universe has given it the right to existence. I will respect all human life, for even that which only lives in my memory will accuse me.”

and

“The span of my life is synchronised to other lives around me. I will not abuse the power of the College to break that synchronisation.”

We are also told that no time travellers from different periods may encounter each other.
The Code is enforced by the Register, the artificial intelligence that Morbern set up to govern the College, and College personnel are so used to it that it is easy to forget the Code is not (a) something that happens automatically or (b) law. Laudable though it is, there are some — even within the College — who might dare to suggest that it is too restrictive.