Intimidation factor.
Does anyone actually believe that the California legislature is really planning to enforce such stupidity? In order to enforce such an unbelievably off the wall "law", the CA State Police, Various County Sheriffs, and local LEO's would all have to collectively violate your 4th Amendment rights in order to "catch" you with "illegal" magazines. They would have to have you under tight surveilence, actually photograph or videotape a sale (or purchase), or otherwise witness such a transaction. Furthermore, they would have to search you at the local range (a violation of the 4th), or in your vehicle (ditto), or in your home (big ditto). Then what? So let's say they actually did catch you. Do you think that such a clear violation of your 2nd Amendment and 4th Amendment rights would ever stand up in court? Especially if you have no prior felony convictions, were innocently not bothering anyone, or were harrassed into an arrest. In addition, the "law" was supposedly drafted and passed to reduce crime, not harass innocent American citizens. What an argument that would be to any Supreme Court.
The true objective of banning "assault weapons" and "high capacity magazines" is singularly apparent and obvious. That is, to eventually make the citizen army (the militia as defined in our Constitution), impotent! That's the motive, that's the agenda, and that's the goal.
American citizens need not obey laws that violate their Constitutional rights! Doing so is submission to oppression.