You are wrong.
ALL banned/illegal magazines and kits that existed inside CA prior to the ruling with judgement BECAME LEGAL immediately following the ruling along with newly manufactured and imported all capacity magazines.
ALL capacity magazines in possession/purchased before the stay was granted (4/5/19) REMAIN LEGAL even now.
After the stay was granted, new purchase/manufacture/importation of larger than 10 round capacity magazine became ILLEGAL as we wait for 9th Circuit appeal, but the LEGALIZED all capacity magazines REMAIN legal for gun owners who possessed/purchased before the stay date.
And CA currently does not prohibit the USE of lawfully acquired larger capacity than 10 round magazines.
CRPA legal team clarified this in detail in this post -
https://www.thehighroad.org/index.php?threads/happy-days-in-ca.849757/page-4#post-11102503
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II. CAN I CONTINUE TO POSSESS THE MAGAZINES I LAWFULLY ACQUIRED?
YES!
III. CAN I USE THE MAGAZINES I LAWFULLY ACQUIRED AT A SHOOTING RANGE?
YES! For the same reasons above, California does not currently prohibit the “possession” of magazines capable of holding more than 10 rounds. Only activities involving the manufacture, importation, sale, transfer or receipt of such magazines are prohibited. The mere “use” of a magazine at a shooting range, for example, is not specifically prohibited.
IV. CAN I CARRY THE MAGAZINES I LAWFULLY ACQUIRED WITH A FIREARM PURSUANT TO A CARRY LICENSE?
YES, but your local licensing authority’s policies may still restrict such activity (Same "no gun" areas prior to ruling). As noted above, California law does not prohibit the “use” of any “large-capacity” magazine."