Aside from the security issue, it seems like an awful idea for a government (or governments, in this case) to say 'hey, you need to follow this standard for invoicing. But also, you have to pay to see the entire standard'.. almost feels like extortion a bit
But yes, for commercial offers, presumption of conformity mean you have to pay for norms to adhere to law. Big fail.
Especially since non-commercial but persistent and public, not "for profit", is still surmised in e.g. warranty laws. (E.g. geschäftsmäßige Nutzung / usage with said two terms, even for F/LOSS)