As a DAR we certainly cannot "do what we want". We each have an FAA advisor who can, and will, overrule a decision we might make in the field. If a DAR is trying to impose what you fell is an unacceptable requirement, you get his or her advisor's contact info and talk to that person. If that person doesn't give you the answer you think is correct, go to that person's supervisor or the FSDO or MIDO manager. If you still don't get the answer you feel is correct, you call EAA and it gets elevated to the national level if need be. Sure, it's often easier to just comply with the inspector's demands if it isn't a big deal to do so, but if the inspector is being unreasonable or is flat out wrong (and yes, that does happen) you shouldn't have to suffer for his or her ignorance or bully pulpit. DARs should NEVER make a unilateral decision on denying or delaying a certificate issuance if it's a question about "approved" installations or the like. They should coordinate with their FAA advisor and come up with proper documentation to support their position, or they should stand down. They can't make it up as they go along.