General Geoff said:
The Bill of Rights supersedes international treaties insofar as applicability to the People of the United States.
However the Bill of Rights is interpreted by the SCOTUS which in Heller (the 2nd held incorporated by the later McDonald case applying Heller to the states) made it seem as if registration is not a violation of the Constitution.
In fact DC was basically ordered by the SCOTUS to allow the person to register and go through some sort of process to own firearms.
Currently the legislation prohibiting registration at the national level is the 1986 FOPA. Not the Bill of Rights.
That part of FOPA could theoretically be undermined by a treaty without violating current SCOTUS interpretations of the Bill of Rights. It would only be altering legislation passed by Congress, not the Scotus interpretation of application of the Bill of Rights.
As for Gun Walker, the motivation behind that appears likely to be increased gun control and restrictions for US citizens after demonstration of the problem they insured was allowed to happen.
That motivation and likely outcome is the biggest reason those involved deserve to be called on all the resulting mayhem, like the death of people shot with the firearms they made sure were sold and even told FFLs they could not refuse selling.
However I must note that within that operation the ATF was targeting people involved in foreign problems, and not regular US citizens and their guns in that operation. The use of their resources on such an issue rather than targeting FFLs and regular citizens over minor issues as is more typical would seem a more desirable situation.
Now the embarrassment from this situation is likely to cause them to focus less on such activity and more on regular US citizens, minor FFL paperwork errors, and similar familiar areas that are legally safer to conduct.
This means more of their resources will be available to harass regular gun owners and FFLs, not as busy monitoring drug cartels and the border.
A government agency wants to demonstrate the need for their existence and funding by showing results, in the form of arrests and prosecutions. If those arrests and prosecutions cannot be for actual serious offenses, then they will be from exaggerations and prosecutions for technicalities.
Now more of those results will have to come from people that make honest mistakes, or minor clerical errors doing things like abbreviating when they were not supposed to.
FFLs should expect more audits and harassment in the future.