I'm guessing that the difference is that these codes are not actual law. For example, in the electrical world, the relevant code in the USA this is NFPA 70, National Electrical Code (NEC) from the NFPA, but these are just codes -- they are not law per se, but may be used to apply related legislation.
In the UK, the code is BS7671 from the IET with related publications about specialist installations, but the law which governs the application of them is the Electricity at Work Act, 1989.
Did your local jurisdiction adopt NFPA 70 or NEC? If so, the presiding judge in the 5th circuit case stated this:
"The issue in this en banc case is the extent to which a private organization may assert copyright protection for its model codes, after the models have been adopted by a legislative body and become "the law". Specifically, may a code-writing organization prevent a website operator from posting the text of a model code where the code is identified simply as the building code of a city that enacted the model code as law? Our short answer is that as law, the model codes enter the public domain and are not subject to the copyright holder's exclusive prerogatives."
The NEC and NFPA model codes (i.e. NFPA 70, NFPA 101) are most certainly model codes that fall under the ruling.
NFPA Link has terms of service that are due to the "model code" being proprietary. Accessing the content via that NFPA Link endpoint puts you at the mercy of the terms of whatever the private third party offers.
But as the law stated, once the code is adopted, it becomes public domain. I would guess that NFPA has no legal obligation to offer a "public domain" portal, so the question becomes at what cost should local governments buy server space and host the texts and make the code available to the public domain? Especially because it appears they are legally obligated to do so? My research shows they currently don't offer it.
I find this kind of like "right to repair" except to "right to access public domain code text." In this case, the right exists, but no endpoint exists, so if there's no endpoint, does the right really exist?
What is the reasoning that they are obligated to provide it? I'm no expert in this area, but I don't think the fact that they are public domain means they are obligated to provide them to you? Is there a separate requirement on law text that says they must be provided? (It would be sane for that to exist, but...)
You could try FOIAing them or suing them if you think there is an actual obligation.
I don't believe code publishers are obligated to publish their model code. Especially because the local jurisdiction might adopt amendments that differ from the code they wrote and control.
Therefore I think they are perfectly ok offering a generic endpoint to the general public as a convenience, and have no liability when the adopted code might differ from what they provided.
From the government side, I believe that since the courts determined that adopted model codes are public domain, they are obligated to publish the code. Is the government required to publish text version of all applicable laws?
In the UK, the code is BS7671 from the IET with related publications about specialist installations, but the law which governs the application of them is the Electricity at Work Act, 1989.