I mean, you need to expand this statement, because with just those 5 words it's blatantly untrue. There's a whole load of mods allowed by my insurance and I'm sure you'd consider most of them "modding" - the law also has no opinion on most of them unless they start changing the emissions of the car(in which case that's still not the end of the world, you can get the car re-certified for the new emissions figure).
You're being pedantic. Saying "modding cars is legal" doesn't mean it's unrestricted.
Since when do insurance companies approve car mods? And what does that have to do with something being legal?
The only federal legal restrictions are on emissions equipment and safety equipment like seat belts and airbags. Some states have additional laws like tint limits and exhaust sound limits.
Wait, I either misread his comment, or it was changed after I replied - I was replying with the assumption that he said "modding is already illegal".
And any mods have to be reported to your insurer in the UK, even if it's just changing rims or putting on non-standard size tyres - failing to do so might get your claim denied if you ever file one.
Also, at least in the US, there is little chance an insurance company could deny a claim based on a mod (reported or not) as long as said mod could not reasonably be construed to be the cause of the claim.
Not that they wouldn't try.
Same as the whole "warranty void if seal is broken" nonsense.