4th Amendment, unreasonable search. And of course the 2nd, but the former is more worrying. Also if printing is speech, then you can add the 1st to the list as well.
The 4th amendment has probably been the most eroded of all the major private liberty amendments, in my opinion. It is, at this point, a pretty worn fig leaf.
Following a post on HN a few weeks ago, I bought a used one to use in the kitchen for scaling recipes. It has to be a linear one for that, not circular, so you can set it and read it without touching it again. I also have one in my "apocalypse kit" in case of, I dunno, an EMP?
My dad was an engineer in the slide rule era and taught me how to use one when I was a kid. He said when he was in college all the engineering students had them hanging from their belts in leather sheaths like gladiator swords and they would slap when they walked.
And the fact is that there's been some level of security since the 1970s or thereabouts after a fair number of hijackings. Any serious debate is about restrictions around liquids/knives/etc. (Some of which related to isolated incidents like the shoe bomber and others of which seem like pretty clear overreach--like I can't bring a hiking pole in carryon.)