Ah, that's quite interesting! I'm going through a similar process of formalization, but starting from Wikipedia (but law did indeed cross my mind as a good candidate for formalization too).

I'm also starting from a set-theoretic-like starting point, but am using Discourse Representation Theory to express it in a higher level language that is a subset of english.

https://code.sgo.to/2021/01/06/brazil.html

Find on twitter in case you are interested in telling me more about formalizing the constitution?

https://twitter.com/samuelgoto

FWIW, metamath looks really awesome, will look more closely into it!