I don’t know of any country where emulation is illegal? Do you?

As the GP pointed out, OEMs use copyright and encryption to protect against unapproved execution. But that doesn’t apply to all systems.

Given countries like the UK and US have the strictest intellectual property and computer misuse laws, and emulation is legal there (bar the aforementioned caveats), I’d be surprised if there was a jurisdiction where emulation was illegal. However if you do know of somewhere then please do share.

The NES itself contains no code. Any NES emulator that ships with no software, or software under proper license (such as homebrew) is unambiguously legal. Does your PC, and the OS that drives it, suddenly become inherently illegal if you, as a user, installed pirated software? No, of course not.

> No, they ruled that the copyright on the API was valid

No, they didn't. They very specifically did not rule on whether the API was protected by Oracle's copyright on Java.

> but that Google's infringement of it fell within the bounds of fair use.

They found that, even if the API was protected, Google's use would be within the scope of fair use, and therefore it was not necessary to decide the question of the underlying copyright.

Here is, in full, the opening paragraph of the decision:

Oracle America, Inc., is the current owner of a copyright in Java SE, a computer program that uses the popular Java computer programming language. Google, without permission, has copied a portion of that program, a portion that enables a programmer to call up prewritten software that, together with the computer’s hardware, will carry out a large number of specific tasks. The lower courts have considered (1) whether Java SE’s owner could copyright the portion that Google copied, and (2) if so, whether Google’s copying nonetheless constituted a “fair use” of that material, thereby freeing Google from copyright liability. The Federal Circuit held in Oracle’s favor (i.e., that the portion is copyrightable and Google’s copying did not constitute a “fair use”). In reviewing that decision, we assume, for argument’s sake, that the material was copyrightable. But we hold that the copying here at issue nonetheless constituted a fair use. Hence, Google’s copying did not violate the copyright law.

There have been cases and a whole project was shut down because of it https://github.com/Bios-Marcel/cordless?tab=readme-ov-file#i...

However this is an entirely different question. Whether or not an API is copyrightable, and whether you'd be in violation for recreating a proprietary API for the purpose of creating an (open-source) market alternative for their product, are entirely different questions to whether or not a specific private company has stopped serving specific customers due to use of software they do not authorize (which they are entirely in the right to do, legally)

No need to. But anything too succesful should be ready to be brought down any moment.

The Pirate Bay, SciHub.

The Internet interprets censorship (legal, moral, or otherwise) as damage, and routes around it.