My logic (against the UN): satellites are subject to international treaties regarding the weaponizing of space. Planes-that-work-like-satellites are less so.I
I don't think this is right. The only governing law on this topic (to date WRT the USA) is the Outer Space Treaty, which makes no distinction between planes, satellites, shuttles, etc. The method of carry isn't relevant, only the weaon's location: "stationed in outer space" and "in orbit" are both specifically banned, in addition to the surfaces of heavenly bodies.
Of course, the boundary that defines outer space is arguable. The USAF definition is 80km, but there are others. Mostly, they're arbitrary lines, kind of like defining "when life begins" when discussing abortion--some have various scientific rationales, but none are universally accepted. Since this stuff has never been tested in a court, it's all really theoretical. So it's all moot, until we see: (1) a body of established case law (plausible, in the next few decades), or (2) a clarifying amendment to the treaty (highly unlikely), or (3) a new, more specific treaty (possible, but the USA has been bricking up recent UN moves in that direction).
So could you launch a sub-orbital weapon under the OST? Dunno. Most ICBM trajectories are sub-orbital, but I suppose that if we're launching live nuclear warheads on ICBMs, treaties don't much matter. (Not much of anything would matter at that point, I guess.) Is a *really* low earth orbit, below 80km, really physically feasible? I doubt it--orbital velocity and atmospheric density are both pretty high, below that mark, so the fuel consumption and heat shielding considerations would almost certainly make the engineers laugh at you.
However, note that the OST only prohibits space-borne nuclear weapons or weapons of mass destruction. Most conventional weapons, HE gravity bombs, ASAT missiles, etc. should all be kosher. And I think there have been public examples of space weapons programs, implemented by OST-signatory nations, that haven't raised any OST-specific hackles. You will probably be OK if you want to:
* Launch non-WMD missiles at satellites, either from the ground/sea, or an aircraft, or an orbital vehicle.
* Drop FOABs or inert kinetic penetrators from spaceplanes onto ground/sea targets.
* Launch non-WMD, self-guided "stand-off" weapons (cruise missiles/smart bombs) at ground/sea, airborne, or orbital targets.
* Carry self-defensive weaponry, for protection against hostile aircraft or orbital vehicles.
And for the record, I believe that WMD generally means nuclear, biological, or chemical, but I don't know how legal that interpretation is. YMMV.
Oh! And I hope this goes without saying, but IANASL.
WP is a pretty good starting point for more details: http://en.wikipedia.org/wiki/Outer_Space_Treaty, or if you're brave, the full-text treaty is also available online: http://www.unoosa.org/oosa/en/SpaceLaw/gares/html/gares_21_2222.html