The CDC goes out of its way to perform gun studies. That is a fact. While what Congress did does not outright ban such studies in the language it does in reality.
It pretty specifically states the research results cannot be used to support gun control policies. Meaning, they are being told what results are ok before doing the work.
Meaning that political and ideological factors are what is figuring out things. Not the best methods and dating obtaining results that is then used for policy. We are blinding ourselves and then wondering what the problem is.
There has been PLENTY of research on guns done by other people aside from CDC. One of the controversies is that gun violence is not a disease, so it's hard to sometimes justify their studies. Regardless, this study WAS authorized by Obama and done upon his request. So, there were some good and bad findings.