When it comes to ordering wireless access points there are a number of important pieces to consider including regulatory domain, antenna selection, and mounting hardware.
Regulatory domains are simply a way of grouping countries that have common policies related to radio frequency equipment (power level, channel set, etc.). If you’re only installing hardware in a single country then you’ll never need to concern yourself with choosing a different regulatory domain. If, however, your equipment spans several countries you need to evaluate which regulatory domain applies to each country. Here’s a link to Cisco’s Wireless LAN Compliance Status page. This page details which products are licensed for use in a specific country as well as which regulatory domain to use when ordering products.
The regulatory domain used for ordering a Cisco wireless access points is simply referred to by a single letter. When determining the part number to order simply substitute the letter of the regulatory domain with the ‘x’ in the product part number.
For example, to order a 3502 (with integrated antennas) for use in Mexico one would change the generic part number AIR-CAP3502I-x-K9 to AIR-CAP3502I-N-K9
Be aware that the regulatory domain can NOT be changed on an existing access point.