There is no code about adding flooring or walkways to your attic.
But rules to remember.
1 Don't change any of the framing
You cannot cut or move any of the framing for the roofing or the deck. Cannot make cuts or alter to make the storage/walkway space bigger (unless those changes are signed off by engineer + inspector)
2 Don't jam the flooring in
Remember that this is not a conditioned space. If you are using plywood and a sheet barely fits... Well when the attic gets 130 degrees in the summer all of that wood is expanding. Wood expanding can move framing and loosen braces (seen both happen). Just give yourself a gap - 1/4-1/2" between framing and pieces.
3 Understand the insulation factor
There are kits that you can buy for attic flooring that basically raises the ceiling joists. These are designed because most attics require about 16" (I do 24" because cost is negligible once you get that far). Well if you just squash blown in insulation it will be about 8-10" high in most houses so it will run short. I would either rollout some fiberglass double layered under or just add blown in over your walkways.
4 Try to mark the walkways
We use flag sticks to mark walkways in attics with insulation. I have seen ribbons on framing and other stuff. Remember that yea you know what you put down but it might be a year or two before you use it.
5 Flooring ends on joists
Might seem just basic common sense... but I have been in attics and step on a piece of plywood flexing and quickly realizing nothing was below it except my foot almost going through the ceiling.
- There is no code against it and nothing you need the inspector out on.