I was once going onto a military post, at a gate where I was searched regularly. After a search, the guard asked me if I had any guns in the car. (There was a gun publication on the back seat.) One half of my brain wanted to ask; "Why do you ask?", but the other half of my brain reminded me that I had a formation to get to and the last thing I needed was to have my 1SG get a phone call regardless of how innocent I was. I just said "no".
Um, WAY NO. An NRA sticker is neither probable cause nor reasonable suspicion that there is a gun in your car. The stories I have read in here recently about guys getting searched (as far as the story explains here) because they had one dropped my jaw. In Utah, I would say this could never happen, but then I remind myself that I have had some experiences with cops (one state university cop in particular) who treated their territory like their own little prison, and did pretty much anything they wanted, including lengthly detainment, and kept getting away with it because most of the time they didn't cite. I had one park, blocking me in, he asked me a lot of irrelevant questions which I refused to answer, and I finally looked him in the eye and told him to cite me or let me go. He said "Maybe I will, maybe I won't." I told him that I needed to go, and I had noticed that he hadn't checked in on his radio, and that his dash cam, if he was running it, would show that I had been there over thirty minutes. (I was pretty sure he had neither called me in nor run the cam. If I decided to claim he had detained me OR done something illegal while he had done it, he wouldn't have a butt-cover.) He grumbled something about us stupid kids thinking we owned the world and left. I never saw him again, my dad asked the university police supervisor about him, he said that they had mutually decided with the officer that it was time for him to leave. I guess someone called his bluff. It was odd, because I usually find older officers are less likely to pull stunts like that. (He was older.)
As far as admissibility of that search from the sticker goes, Is it dirty? You betcher bippie. Will the judge listen to reason and precedent? He might force you to play hard, hire a lawyer, etc.