nodi re your think progress post below....
You do realize that in most jurisdictions the requirements for CCW permits are as you stated.
Fed law is that no one under 21 may purchase a handgun in their own right. By extention that also limits a CCW to those over 21.
Also on the background check for firearms purchase there is a question about domestic violence convictions. If you have been convicted of domestic violence & certain other crimes, or have been adjudged insane you will be denied on your purchase request.