It will obviously be in a very low orbit, because that's the easiest to reach and construct...

Well, for a bunch of reasons, these space data centers probably won't be at very low orbits. First and foremost, very low orbits like the ones starlink uses experience a lot of atmospheric drag. With the huge solar arrays these data centers will need, that high drag environment is a killer. Going just a bit farther out would significantly reduce that drag. Also, latency isn't a huge concern with space data centers, so very low orbits aren't required. Lastly, since those low orbits are so highly valuable and contested, it just doesn't make sense to put something there that doesn't need to be there.

TLDR: Space data center orbits are likely to be somewhere between 500 - 1000 km altitudes.

And yes, that's in untouchable range for anything but advanced militaries.

What it's not untouchable to is legislation. That's the practical way to fight it.