how does U.S. civil law apply to the actions of U.S. citizens, while they
are traveling abroad?  I.E. if a U.S. citizen commits theft from
another U.S. citizen while in Great Britain, is there any cival legal
recourse when both parties return to the United States?

Hello and thank you for your question.

Since this is a civil matter, the suit is between the two individuals
(unlike a criminal matter where the State is one of the parties).  And
that means that the jurisdiction question is a matter of gaining
jurisdiction over the defendant in the U.S. state where the defendant
resides.  So the court is not in any way asserting jurisdiction
outside the country nor even outside the state--the defendant is being
sued in his/her own home state.

Here is a typical state statute (Missouri) that explains it clearly.
You'll notice the second section--jurisdiction in the defendant's home
county where there was a tort that happened outside Missouri [a tort
in New York and a tort in the UK are equally 'outside' Missouri for
these purposes and will get the same treatment]
"In all actions in which there is no count alleging a tort, venue
shall be determined as follows:
....When the defendant is a resident of the state, either in the
county within which the defendant resides, or in the county within
which the plaintiff resides, and the defendant may be found;"
"[I]n all actions in which there is any count alleging a tort and in
which the plaintiff was first injured outside the state of Missouri,
venue shall be determined as follows:
....If the defendant is an individual, then venue shall be in any
county of the individual defendant's principal place of residence in
the state of Missouri or, if the plaintiff's principal place of
residence was in the state of Missouri on the date the plaintiff was
first injured, then venue may be in the county containing the
plaintiff's principal place of residence on the date the plaintiff was
first injured."
http://www.moga.mo.gov/statutes/C500-599/5080000010.HTM

As another example, you can see the Montana statute on page 4 of the
following case (although the case itself is not on point)
www.lawlibrary.state.mt.us/ dscgi/ds.py/Get/File-32602/04-067.pdf

[Again, this is not to be confused with the situation where the
defendant is a foreign person, for example the circumstances when the
plaintiff can or can't take their case to a US federal court;
http://www.millernash.com/showarticle.aspx?Show=414 ]

Search terms used:
resident foreign tort -long
[the -long is to avoid getting the many "long-arm" cases that have
nothing to do with our facts]

Thanks again for letting us help.

Google Answers Researcher
Richard-ga

The court has to have jurisdiction in order to try a case, over the
person and the location.  No US court has jurisdiction outside the US,
with the exception of those terrorist crimes against US citizens where
the US will bring the terrorits to account in US Courts and military
courts who have jusrisdiction over US military personnel no matter
where they are located.