This has nothing to do with Github, other than the fact that Github would let you end-run all rules about data protection, backups, centralized administration of user access, and everything else that you don't individually have to worry about, but the management and IT at the company you work for does.
This is exactly the sort of thing I'm talking about. Let the team working on the code decide who has access to the code. Not some person in a different part of the country who has no idea what the code does.
We have active directory and its all managed there. If someone needs access, their role defines it. If someone wants access they have to ask.
Code theft is a major problem. Not because the code is crap and we're embarrassed (unlike VMware and Microsoft code leaks), but because its valuable.
Do you whitelist or blacklist the internet?
(Good) web services like Github tend to reduce friction, corporate bureaucracies tend to increase friction.