This is just stupid. Why would anyone ask Twitter to do anything of the sort? It's like asking Ford Motor Company "Would you build electric chairs?" Of course they'll say no, just for the PR and to not alienate customers, since they know the government is not going to ask them to build electric chairs.
The fact of the matter is any of several thousand software companies could easily throw together a registry of this kind. It's straightforward stuff. Heck, outsource it to India. They'd have no problem doing it even knowing what it would be used for.