Keeping the records is mandatory. What goes in the records is partly optional. Notice that one of the things the records "may" contain is "authorized arms transfers." Who authorizes them?

Countries that are not participating with all of the "may" stuff, such as "end users," will potentially be shunned and have less cooperative power at the U.N. That is an element of pressure that makes this problematic. Our leaders could use that pressure element to try to justify bad gun legislation in the U.S.

In case you haven't noticed, I am not a fan of the U.N. We have a country and a Constitution here, and we do not need to be answering to other countries. Playing games with the relationship between our domestic laws and the U.N.'s laws is a terrible idea, and I am really suspicious about why this is happening with gun laws.