if it is legislation you seek, you'll need to drum up some support for whatever legislation it is you want passed
The issue is far more important to the USA than NRA and is by no means anything secretive but I just don't want to divert the conversation into discussing it, which will be inevitable. I just need to understand the principle of how to proceed.
How to hire a lobbyist is something pretty unclear to me. Also, it probably requires spending of substantial funds which I don't possess. I'd rather try to convince the US Congress myself somehow, that the inclusion of the mentioned one sentence is needed, and here is where it gets sticky wicket. Your point of drumming up support is well taken and this is exactly where this mediation problem in the OP kicks in. If I can somehow produce before the US Congress a written statement, as a result of such mediation, that what I claim is objective truth and not just my opinion, this may be drumming up more support than any other way that I can think of, because the other party, the party that has made a written statement that what I claim is my personal opinion, is probably the most influential world organization. So, we're back to square one -- negotiations need to be initiated with this organization to resolve the conflict and reach a mutual understanding expressed in a written document that the claim concerns an objective fact, a truth, and is not just personal opinion.