Can y'all build up a non neutered AR on these lowers legally?  I have a few friends in CA and they would love to build one up if they can do so legally.  

Also can someone please provide some documentation behind the legality?  

Much appreciated.

in a nutshell:right now no....the only reason that people can buy these receivers is because they are not specifically banned by name...however if certain features are added(pistol grip detachable mag) then it becomes an illegal assault weapon by definition... if the AWB is updated and the unlisted receivers become listed then people must register them. by having a receiver registered as an assault weapon owners may add whatever features characteristic of an assault weapon that they want...except hi-caps unless these were owned before hi cap ban which im sure they all were!!!

Check this link out.  It pretty much explain everything in plain language.

www.calguns.net/a_california_arak.htm

It works like this.

Step 1: Buy off-list (non-named) AR lower.

Step 2: Build it up as a 10-round fixed (neutered as you put it) magazine self-loading rifle.

IF the CA DOJ adds your lower to the list of banned-by-name ARs, THEN continue:

Step 3: Register the rifle is full accordance with the law, during the 90-day registration period.

Step 4: Build the rifle up like a completely normal AR, complying with state and federal laws (OAL, BBL length etc...)

One thing your friends should do when purchasing the receiver, is intend to build itup at a FAB-10/Vulcan look-alike. Don't count on the DOJ taking any action on this. If the DOJ does take action, it's Miller Time.. if not, you've got a self-built high-quality AR with a fixed mag.

I see it as win-win.