Is it a registered assault weapon? If so, then yes.
Edit: I should clarify the AW laws for pistols. Here they are:
If the pistol is not a registered assault weapon, then no, it is not legal in its current configuration.12276.1
(a) Notwithstanding Section 12276, "assault weapon" shall also mean any of the following:
(4) A semiautomatic pistol that has the capacity to accept a detachable magazine and any one of the following:
(A) A threaded barrel, capable of accepting a flash suppressor, forward handgrip, or silencer.
(B) A second handgrip.
(C) A shroud that is attached to, or partially or completely encircles, the barrel that allows the bearer to fire the weapon without burning his or her hand, except a slide that encloses the barrel.
(D) The capacity to accept a detachable magazine at some location outside of the pistol grip.
(5) A semiautomatic pistol with a fixed magazine that has the capacity to accept more than 10 rounds.
The Intratec TEC-22 is not an assault weapon by name (the TEC-9 is) so that's already in your friend's favor. But it has 2 evil features, the threaded barrel and the detachable magazine not located in the grip. If there was a way to install a magazine lock to make the magazine fixed, then it would be legal as long as the fixed magazine does not hold more than 10 rounds. He would not be able to use his standard capacity magazines with the gun. He would need a 10 round (or less) magazine if used with a magazine lock. If it's registered, then no problem. The magazines are legal to possess if they were possessed before January 1, 2000.