Also, you can't ask anyone else on the team for help implementing it.

These backdoors are going to be the worst code possible. What kind of crap quality code do you think a single dev under threat of jail time and the pressure of not being able to communicate with his co-workers or legal representation is going to pump out?

It'll be handy cover though if you get caught introducing your own backdoor code.

"Git says you were the person who introduced this backdoor into our banking platform. We could loose millions though that. Explain yourself now before I call the cops!"

[whilst tapping nose] "I'm sorry boss I've been told not to discuss that with anyone..."

"Say no more. I understand perfectly. ;) Carry on and don't tell the others."

You can speak to a lawyer about it, though I imagine that delaying might cause issues. There is a mandatory 28-day consultation period for TCNs but I imagine that you'd get very little useful protection from that system.

Also there is no criminal punishment for not obeying a notice. There is massive civil liability though, as well as a criminal punishment for disclosing information about the notice.