From http://www.southwest.com/html/custom...ombine_flights

At this time we are limiting connecting service to international destinations as we roll out new international capabilities across our systems and network. We hope to fully convert the Southwest network to support connecting service to international destinations by the end of 2014.

If you choose to book two separate reservations to connect flights from your point of origin to an international destination and return, please be aware of the following limitations and how they will impact your travel:

You will have two separate reservations and two separate tickets.
You must check in for your flights separately in order to receive boarding passes for both reservations.
Your baggage will be checked to the destination listed on each ticket, not all the way through to your final destination. This means you must:
Leave the secured area of the airport.
Claim your luggage at baggage claim.
Re-check your luggage at the ticket counter to the destination listed on your second ticket.
Proceed back through the security checkpoint for screening.
Arrive at your departure gate ready for boarding at least 20 minutes prior to your next flight’s departure. We may begin boarding as early as 30 minutes prior to your flight’s scheduled departure time.
If you have not arrived at the departure gate at least 10 minutes prior to departure, and have not notified Southwest of your intention not to travel, your reservation is subject to cancellation and your seat may be relinquished to another Customer. You will not be eligible for denied boarding compensation and will be considered a “no show” Customer. Our No Show Policy will then apply.
Because you are not traveling on a scheduled connection and are building your own flight itinerary, some protections afforded in our Contract of Carriage for disruptions will not apply to you or your travel.
If you choose to book reservations in the manner, we suggest you allow no less than three hours between flights.
Make sure to check back often as our schedule changes frequently and connecting service may be available in the near future.

REALLY? Who would subject themselves to such torture, risk of MAJOR HASSLES during IROPS?