Laur, if someone told Uncle Sam that, say, Lockheed was selling F16 components to the Chinese without the government's explicit OK, they'd bring an awful lot of pressure to bear on LH and it
would stop. The key is how important the issue is to our government. Not much they could do about stuff already out there, but they could choke the supply.
With Russia, the issue may be a lack of information or lack of control of the situation since the collapse of the Soviet Union, a deliberate thing, or it may just be a lassez-faire attitude. In most cases, I think they could do something about it if they wanted to.
I did notice that Russia is a little upset because they think some of our spyplanes are flying too close to their airspace, though. Hmm... A tool of statecraft?
