Y'know... it might be worth the trouble to stage a nice demonstration for the court. The result would be a video showing how wrong police and the public can be about the law.
Imagine seven rifles on a table and you ask five different police officers to identify the CA-defined "assault weapon"[¹]. Do the same with three or four civilians. Among the rifles should be one true (legally registered) "assault rifle", a .22LR version, a modified rifle with no pistol grip, a (likely borrowed) Class-III M16, a CA-compliant "fixed magazine" rifle with a collapsing stock and bayonet lug and two CA-compliant "standard" AR-15 pattern rifles.
For non-Californians - CA has two (2) statutes. The 1989 law lists specific makes and models - such as the Colt AR-15 and Bushmaster XM15 - by name. After names were changed, CA added a "ban by features" that included things like a pistol grip, detachable magazine and any one of a list of features (bayonet lug, flash hider, collapsing stock, etc.)
In the demo above, the .22LR version is exempt because the law deines an AW as a "centerfire" rifle. Likewise, without a "protruding pistol grip" the rifle does not meet the definition under the "features" ban. The actual M-16 is not a banned "assault rifle" but a "machine gun" in CA. The "bullet button" mentioned requires the use of a bullet tip (or similar probe) to release the 10-round magazine which qualifies as a "fixed" magazine and exempts the rifle from the AW statute.
¹ "Assault weapon" as defined by CA law, not by military arms terminology the rest of the world uses.
BillCA in CA (Unfortunately)