The CDC WISQARS database contains fatal and non-fatal injuries for many different mechanisms, including firearms. The law you are thinking of is the "Dickey Amendment" which forbade the CDC from spending its budget advocating for gun control. It was named after Republican and galactic asshat Jay Dickey of Arkansas, who thankfully has been removed from influence over national politics by his much-awaited death in 2017. His idiotic law passed out of effect in 2018. Just before he died, in a meaningless act which did not redeem his evil life even slightly, he recanted and called for government funding of research into gun violence.

How would the CDC be allowed to advocate political positions contrary to the constitution, and without congressional approval? As far as I know, it's at least looked down upon when federal agencies advocate that sort of thing, even in roundabout ways.