I did it for four years with a company out of VA. I enjoyed it, had some good times and worked with some good guys, both LE and Mil.
The main reason I went was that I was Infantry back in the 80's, and never got to deploy into a combat zone.
There are, or were, rather, several companies employing experienced LE for training, advising, and mentoring coalition and "allied", Iraqi/Afghan police/military. I believe that most of the good contracts are gone now, but you may be able to find something.
I would try to avoid DynCorp if possible, as their hiring standards were lower, they paid less, and I think those guys had to pay for their own plane tickets when going on leave.
Overall I personally really enjoyed it, I got to spend time in Iraq and Afghanistan, work with some different military units, and act like my old ass could keep up with the 18 YO kids on missions.
My absolute favorite time was my last year advising the AFG NP undercover unit. I got to work with different ISAF SOF units and see how they did things as well as play with some cool toys.
If you have any questions, feel free to send me a PM.