Near as I can tell, there is no explicit legal limit in Germany. Like the US it’s a kind of ‘soft’ limit, and is about 12%. If someone can find where it’s codified in law, I’d appreciate it.

Pretty sure I can buy 30% or more from a lab supplier in the US. I can buy gallons of the 3% stuff with no issue too. The 12% stuff is usually in hair products, which I think has stabilizers or other additives in it. I use peroxide for European style mounts which is why I need so much of it. I decided 3% works fine and is way more economical than the powerful stuff even if it takes longer.

Well, you can buy pretty much anything from a lab supplier if you’re the right type of customer.

It's EU law, 12% hydrogen peroxide is the highest you can get in EU without being cleared to do so (say by showing government authorization, proof of end use, proof of academic education or certifications, ...) [1].

[1] https://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:...