If someone who is in the IRR has their clearance revoked in their primary MOS, can they reclassify into the USAR?

A revoked clearance is a show stopper that has to be addressed before transfer. Not having a clearance for your mos or going beyond 5 years for a ts or 10 for a secret is also a show stopper. A person is transferable, however, if they do not yet have the required clearance that they are trying to "will train" into.

SGT James Miller The best option for you friend is to have them sit down and talk to their local Career Counselor. That way they can be make sure they are given the most accurate information, when the counselor is able to look up all their information up in the system. If you want to send me a private message I can assist you with finding a local Career Counselor for your friend.

Also, he talked to a Reserve Career Counselor and she mentioned the revoked clearance and it didn't matter if he wanted to RECLASS, but she didn't know why. She said her battalion would kick it back for some reason. She said to call Reserve Security Clearance hotline (it's at HRC at Fort Knox, KY). He called and the guy on phone only confirmed the clearance being revoked for a year or so now. My friend told him what he was trying to do, and he said it's because, if the Army want's him to go back to his first MOS, that would be a problem, so No Go. Now, I listened to both conversations with him via speakerphone.
To me, it doesn't make much sense to me since, at least with Active Duty: "Re-enlistment Prohibition code 9P (loss of MOS qualification), and be processed for mandatory reclassification." I couldn't find the reference easily, but reclass someone involuntarily (maybe; up to chain of command) but, no: voluntarily.