"A question, particularly for those who support free markets:

At what point does a legitimate, (i.e. done without force) financial transaction become a security threat? Where can the line be drawn? Is there an objective standard that can be used? Obviously, China buying up Boeing or some other major defense contractor is a red light. China buying up Chuck E. Cheese isn't. Where does oil fall?"

Gosh, as far as I remember all these types of trade restriction were brought about as response to the Union Soviet. Last time I checked, we won that war over a decade ago. It would violate current laws, but other than that I don't see a problem with selling Boeing to China.

"Would it matter if the country was Switzerland instead of China?"

Nope, because once you sell it to Switzerland, what is stopping them from selling it to China? As I said the Cold war is over and so is the cold war alliance. I see no reason for these current American laws except for the stupidity of Congress being unable to change them.

Now, there are problems with China in regards to copyright violation, human right abuses, threatening Tiawan, etc. But we need to change these laws on the books that were put there because we were fight an aggressive nation with close society with 10,000 + nukes pointed at us.