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Have you never had a girlfriend? Sometimes you apologize when you aren't in the wrong so you can keep the peace.
In any case, airspace is often a de-facto area of international law. China can say "you're not allowed to do that!" All they want. But the US did it. >

Airspace is not international law. A state has complete and exclusive sovereignty over the airspace above its territory. It’s why the balloon was shot down over the coast in American airspace. 
A quick google search can confirm this. >

Yea, isn't your airspace as high as you can enforce? Or something like that >

There's no firm upper boundary so far, except insofar as objects in orbit are not considered to be within any nation's airspace. >

So roughly the Karman line, which is itself not precisely defined. >

I believe the 100km Karman line is what is used for treaties and such. Which ya is kind of nebulous since you can find sources that'll say the Karman line is at 80km. >

The 100mk line of demarcation has been historically used dating back to the space shuttle program and before, but the argument has been put forth for years now that the line should practically be lowered to 80km because the line was always supposed to represent the last point at which there was any significant atmospheric density to support aeronautical flight as opposed to ballistic. 
Not that aeronautical flight is particularly likely at that altitude. But it seems that experts wanted to delineate the point at which satellite orbits decay and meteors begin to burn up due to resistance (which happens at 100km), and the highest extent where winged craft and balloons can possibly reach while still riding on air. 
Another part of the argument seems to be that depending on location on earth, season, and temperature, the line can vary slightly, and by going with a figure of 80mk we set a consistent minimum across the board. 
I suspect that 80km will be the official karman line of the future. >

TIL thank you!
It's funny when the laws of man turn to science and ask for a hard number only for science to go "well ya see it's a spectrum" >

This is why we should distrust so-called scientific evidence that purports to give absolute answers. Very little is truly absolute in this physical universe we find ourselves in. While not particularly satisfying when looking for the cut & dry, scientific answers should tend to take the form: “Under condition A, 99.9% of all observed X will Y, provided that B is C.” >

regardless if it was military, or spy or just a weather balloon. its our airspace. 
if china wants to float their crap over here. then they need to ask for permission. >

A weather balloon is acceptable without permission, under international laws to which the US subscribes. 
The legal question here is whether this dirigible meets the standard of “weather balloon”, which is looking increasingly unlikely… >

That changed recently trump pulled out of that treaty didn’t he ? >

The Open Skies treaty is entirely different, and governed the scheduled over flights of electronic intelligence gathering aircraft from adversary countries. It was primarily between the US and Russia, and Russia was no longer complying with their end. >

How would we know of such a balloon had chemical or bio weapons that would be released upon being shot. And did we know before we shot this one down. >

Most chemical weapons require a certain level of concentration to be effective. Dispersal at 60,000 feet would mean that by the time any agent reached ground level it would almost certainly be below the required concentration.
And would be considered an attack with a WMD. And the US's current policy is to treat any attack with a WMD as a nuclear strike...which would require nuclear retaliation. That's a line no one is going to cross...with a balloon. >

Interesting. Obviously I don’t know about this stuff. Was just wondering, thank you. >

The fact that the Chinese are asking for it back clearly meant it wasn't a civilian weather balloon as they claim >

That's rich given how they basically got a EP3 Aries from us for free about 22 years ago, after one of their fighters collided with it in international waters.