As I understand FEDERAL LAW...
You cannot buy from a Federal Firearms License(FFL) holder if you are under indictment for a felony. There are additional limitations also....
I don't like the fact that you are considered guilty by the BATFE BEFORE a conviction but that is the law.
If you have DEEP Pockets feel free to challenge this in court since you have standing as you have been refused by the FFL to make the purchase.
Also, Please don't confuse the Federal restictions on the purchase of a handgun from an FFL and any STATE based restictions on the issuance of any Conceal Firearm Permit.
And remember, this is NOT LEGAL advice and I am not a lawyer.