No matter, I found the way to do it. For those of you who wants to do the same, open the admincp/admin_banlist.php and find the following line of code on line 101:
Code:
if(!is_member_of($vbulletin->userinfo, 6)){
Replace this with:
Code:
if(!is_member_of($vbulletin->userinfo, 6) and !is_member_of($vbulletin->userinfo, 29)){
And just change the 26 into the usergroup that you want to give permission to. Obviously, you can add as many groups as possible, by just adding the code into that line, as I've done above.