It is legal to reverse engineer an IC.
And it is legal to
manufacture an IC that was created from knowledge generated from reverse engineering an IC.
But it is illegal to
sell anything that contains IP that has not been properly licensed. (so you can make the chip, fill warehouses full of them if you like, but you can't legally sell them or do anything with them)
That is why Intel, and every other business, applies for patents. It doesn't keep you from making knock-offs and cheap imitations of their products, but it does prevent you from legally selling them.
Yes everyone who wants to know already knows the "secret" formula for Coca-Cola. And they can manufacture it to their heart's delight, but they can't sell it (which includes giving it away) because they don't have a license from Coca-Cola to sell their IP.
Reverse engineering is great if you (1) aren't worried about the legal ramifications of selling your product without licensing the IP, or (2) aren't going to necessarily re-use the IP, but rather are going to use your knowledge of the IP to then seek out alternative ways of doing the same thing (the "learn by example" method of self-improvement

)
So, given the mammoth costs associated with reverse engineering a billion transistor IC, and the limited value to come from doing so, it is not really worth any business's time and money to do it that way.
Motivation via national interests are different though, as is the resourcing and cost-benefits justification.