Although I can't find anything specific about this, I am sure from experience that the access-list is applied to both interfaces because of the way that the firewall simply passes traffic through the interfaces, as they are not seen as a hop, nor do they have IP addresses allocated to them. If the access list has a source and destination, in theory it doesn't matter which way the packet travels it will still be seen and thus inspected on both interfaces.

I hope that this has been of some help, sorry I couldn't be 100% on the answer, but as I said, from experience I believe this is correct.

If you want any forther information, there is quite a lot of documentation on Ciscos site:
http://www.cisco.com/en/US/products/ps6120/tsd_products_support_series_home.html
and something you might be particularly interested in is:
http://www.cisco.com/en/US/docs/security/asa/asa83/asdm63/configuration_guide/config.html
This is the configuration guide for ASA5500 via ASDM.

Hope that this has been of some use to you :)