Put a cat in a context in which it's subject to the authority of another entity and that specific cat might well find that it is expected to behave in a specific way toward mice -- either to kill them or not. And that the cat might be rewarded and/or sanctioned based on that activity. I'm not arguing that this is a
legal context, but that rights and obligations exist within a power and control context, which might or might not exist.
Regards C-W, your quoted passage states specifically "unless in respect of our own citizens". Which is to say that U.S. law, under C-W, can specifically govern the actions of the US and/or its citizens.
The recent record also seems clouded. There have been individuals whose extradition to the US has been sought (or secured) for actions occurring principally or totally outside the U.S. The case of Manuel Noriega comes to mind:
http://en.wikipedia.org/wiki/Manuel_Noriega#Criminal_prosecu...
"In April 1992 a trial was held in Miami, Florida, at the United States District Court for the Southern District of Florida in which Noriega was tried and convicted on eight counts of drug trafficking, racketeering, and money laundering."
There's also Executive Order 12333 2.11:
"No person employed by or acting on behalf of the United States Government shall engage in, or conspire to engage in, assassination."
http://www.archives.gov/federal-register/codification/execut...
http://www.cnn.com/2002/LAW/11/04/us.assassination.policy/in...
http://en.wikipedia.org/wiki/Executive_Order_12333
Further, your use of C-W doesn't support your previous statement: "[The Constitution] does not limit what the United States can do abroad". It simply states that there do exist powers which, even if not explicitly listed in the Constitution, would exist. Not that the Constitution could not specify, define, and/or limit such powers.
Which in fact it does -- the United States cannot engage willy-nilly in international agreements with other nations, or engage in acts of war. Both of these require specific actions of affirmation vested in the Legislature: Declaration of War by the full Congress, treaty approval by the Senate.