US Rules do not address the issue sufficiently.

6.6.1 Each sailplane is prohibited from carrying any instrument that:●Permits flight without reference to the ground.

Approved Instruments with Aritifical Horizon or T&B Features, the only approved instrument in the USA is the Butterfly Avionics Vario. Many other instrument have these features and are not approved.

I competed in a National Contest several years ago. I showed the officials my Air Avionics had been disabled. I also asked the official how he was going to ensure all AHRS were locked out. The CD announced at a pilots meeting that no checks will be made for AHRS disabled in the contest. Again if you are not going to enforce the rules get rid of them.

Richard