You might try the IDPA Website at www.idpa.com
. In the FAQ section, a question is posed about the legality of Ashley Express sights. The answer is that since they are considered to be of standard notch and post design, they are allowed.
Since your abbreviated ghost ring is nothing more than a wide notch, they should be perfectly legal for IDPA.
Since I'm not on the IDPA Board, all standard disclaimers apply.