Wifi 5GHz AP Mode: What does `no IR` means and can I bypass it?

As you correctly noticed, this has to do with the regulatory domain. It is both, set by the hardware (pre-programmed for use in ...) and by the userland (iw / CRDA [Central Regulatory Domain Agent, a udev helper]). The thing is, you can only lessen the spectrum of available channels.

Lookup current RD: iw reg get
set RD: iw reg set <CC> with being the ISO_3166-1_alpha-2 2-character code for the country you want to set.

Explication

Linux allows changing regulatory domains in compliance with regulatory restrictions world wide [...]. In order to achieve this devices always respect their programmed regulatory domain and a country code selection will only enhance regulatory restrictions. [...].

Example

If your device was programmed for operation in the US (which allows operation on channels 1-11 on the 2.4 GHz band) and you visit Japan (which allows operation on channels 1-14) and you change your regulatory domain to JP you will not be able to use channel 12, 13 or 14 (CCK). But if you have a device programmed for operation in Japan and visit the US and you select US as your regulatory domain you will have channel 12-14 disabled.

http://wireless.kernel.org/en/developers/Regulatory/CRDA#Using_iw_to_change_regulatory_domains

To bypass regulatory restrictions enforced by your hardware, and according you have good reasons to do that, you can patch your driver. I recently wrote a post about that regarding Atheros chipsets.