It depends on the code. You can’t copyright something functional like a for-loop. What you can copyright is the larger expressive, and arbitrary, structure of that code.

Copyright is not meant for utilitarian purposes. For that there are patents. The non-utilitarian, artistically expressive aspect of software is in how code is organized. You know, the rather arbitrary decisions that spawn hours of bike-shedding.

Copilot is most useful when it makes no creative decisions and instead follows the style and design patterns already established in the code base.

you are assuming some imaginative scenario. "Hold up" in court. It will never happen. Just check how many ways you have to write a method to check if a number is odd or not. If you are using a application using a framework, pretty sure all codes looks similar. Look a ruby on rails application for example. Quite often, the user model, session controller and in some level, all controllers if they are following the "rails way" they look very similar.