Car modification laws, compared by country

The same modification, judged by four different legal systems. 48 modifications across the United Kingdom, United States, Germany and Norway, with the rule that decides each one and the primary source behind it.

16 of these 48 get a different answer depending on where you drive. A regulator can only publish its own rules, so this is the view none of them can give you.

Sources last reviewed July 2026.

Verdicts are generated from the same researched country rules that drive the individual legality guides, so a row here always matches its full guide. This is general information, not legal advice. The US column summarises federal law where one exists and the common pattern across states where it does not. Sources last reviewed July 2026.