Parent companies should be legally held accountable for their subsidiaries though.

The thing is we do this with citizens all the time. For example if a citizen of my nation goes and commits pedophilia overseas they are still prosecuted for it. Similarly of they commission a third party to commit a crime for them.

This is something we are beginning to see in an international context with companies that commission crimes such as the landmark Lundin Petroleum (a Swiss company) trial last year, over corporate complicity (incitement really) of human rights abuses in Sudan.