If it was a stock mini-14 with no pistol grip, folding stock, flash hider, bayonet lug, grenade launcher or anything before the 9/13/94 effective date of the ban, then it's illegal to add those features now, regardless of when the rifle was made or bought.

However, if it's been solely in your friend's possession since before the ban, then who's to say he didn't try a flash suppressor on it at some time before the ban, or taped a pistol grip to it for kicks, or put it in his closet in a box with a pistol grip or folding stock?  Any of those actions on or before 9/13/94 will make it a grandfathered "aw" and he could now re-add all the evils he wants.

Should be no problem at all.

Ok the MINI-14 is differnt from most firearms in the 1994 ban. The Mini-14 minis a folding stock is exempt from the 1994 ban. So you can take a new mini-14 and add on a pistol grip stock, flash hider, bayonet lug and still be legal as it is exempt from the ban without a folding stock. But if it has a folding stock on it then it falls under the ban. I would say to your friend get a fixed butler creek stock and add all of the rest of the stuff. The folder kinda sucks for them anyway. There is a list of firearms exempt form the ban that aslo includes the Iver Johnson 50th anneversry M1 carbine. Along with several others.
SCAR

SCAR, I don't pretend to be an expert on Mini 14's, but I would be interested in knowing the source of your information. Aren't a sufficient collection of "evil features" on any rifle manufactured after Sep 13, '94 illegal? I have seen nothing that would allow adding those features to a Mini 14 built last week, though I know it starts out with one less "evil" than the AR15, since a standard wood stock Mini does not have a pistol grip.

I'm gonna guess that the gun needs to be "manufactured" prior to 11/89 and the AW ban to be exempt. The way I read the law that means it needs to conform to factory specs out of the box and NOT according to some hypothetical "pre-ban" personal modifications.

But don't quote me. I'm no legal beagle.

I see a lot of "pre-ban" mini-14's with all sorts of stuff on them.

Unless you live in Kalifornication the year 1989 means nothing.
Unless Roach Island has some sort of anti-gun laws the following applies in the federal sense:

US CODE 44
TITLE 18
CHAPTER 44
SECTION 921

(B) a semiautomatic rifle that has an ability to accept a
detachable magazine and has at least 2 of -
(i) a folding or telescoping stock;
(ii) a pistol grip that protrudes conspicuously beneath the
action of the weapon;
(iii) a bayonet mount;
(iv) a flash suppressor or threaded barrel designed to
accommodate a flash suppressor; and
(v) a grenade launcher

So, if the mini-14 in question had any of the "assault weapon" features before the ban then they can be added after the ban and it's legal.

Rule of thumb:
Use any post-ban AR15 as a guide.
a semiautomatic rifle
ability to accept a detachable magazine
a pistol grip that protrudes conspicuously beneath the action of the weapon

You can set up a mini-14 the same way.
With a pre-ban you are able to use all items.

IF I were your friend with the mini-14 I would just do it.

There is a book called "Gun Laws of America with plain einglish summeries". And in this book it explanes the laws in terms we can understand. Well there is a list of firearms that are exempt from the 94 ban I will try to scan the law about the 94 ban and also the referanse to the list along the list of exempt firearms.
SCAR

SCAR, sounds like the publication only tells half the story. There is another part, and Clearfire quoted it above. 921 applies to all weapons, even a Ruger 10-22 as well as to Mini 14's, AR15's and M1 carbines. A detachable mag and one evil feature is legal in a postban gun--but a detachable mag + two features is an AW in the eyes of the 94 law and illegal to assemble into that configuration after 9-13-94 even though the gun may have been built before that date without the features, as were Mini 14's. This isn't easy to understand, and lots of people don't, so don't feel bad if it's not clear to you. Many intelligent people are still debating this as we speak. If your friend had already configured the gun into AW form before the ban, no problem. But if they bought the stuff after the ban, whether your friend does it now or not is a personal choice, but it would definitely be illegal under federal law. He/she would be adding 4 features--the folding stock, the pistol grip, the f/s and lug-whereas the Mini 14 starts out with the detachable mag which qualifies it to have only one of the additional 4.  

Like said before no problemo on this one.

For those of you that are curious about the Mini-14 exemption, please refer to the list in APPENDIX A of TITLE 18, USC, section 921, the Mini-14 is on the list.  In section 922(v) (3) it states "(A) Paragraph (1) shall not apply to- (A) any of the firearms, or replicas or duplicates of the firearms, specified in Appendix A to this section, as such firearms were manufactured on October 1, 1993;....."  what ever the heck that means?

That little snippet means that the named guns, as they came from the factory (i.e., all standard models) on 10/1/93 are exempt from the ban.  If Ruger made a factory folder with a factory flash hider, and that model was identified in an exemption, it could have a folding stock and flash hider no matter when it was made.  You couldn't accessorize such an exempted weapon beyond the factory model, though, nor would that allow you to have a flash hider on it in cali, for instance.

If he owned it before the ban and bought and installed it all before the ban, there should be no practical problem. Receipts dated before the ban for the folding stock, etc would be nice but realistically how many of us have them. People who buy "preban" guns after the ban and then start adding stuff are the ones who MAY repeat MAY have a problem with proving when it was configured with AW features. Guess the moral of the story is don't sell the Mini 14's you've owned for 10+ years.