U.S. v. Miller loosely established the test (later solidified in 2008's Heller v DC) that weapons commonly used in militia service are inherently deserving of second amendment protections.

Miller, a known mobster who was caught with a sawed off shotgun lost his case because

a) the military testified that they had never used sawed off shotguns, so they were not useful to a military, ergo a militia (which was a lie -- they had used them, and found them useful for trench-clearing)

b) Miller's attorney was not very good, and didn't even challenge that testimony, much less so by totally disproving it -- I offer a little sympathy here as they didn't have Google at the time

Also noteworthy, Miller was actually dead when the decision came down, as he'd been murdered, and because /shrug, the trial kept going, but the defense (for obvious reasons) quit trying. He was sentenced in absentia.