I'd have to confirm with buddies who are the SMEs on this, but believe there's already past precedence on the issue of backdoor banning, where implementation of taxation or fees make exercising a right not realistically affordable.
That's not to say that it won't be tried or pushed, but it's been tried before.
You may be referring to CA passing a law to require background checks on ammunition purchases -- Proposition 63 in 2016.
Or maybe the one that CA passed restricting "handgun ammunition sales" by requiring face-to-face sales, thumb prints, registration of buyers, etc -- AB962 in 2011.
Or perhaps the tax on guns and ammo -- AB 1223 in 2021.
CA keeps proposing and passing bills and propositions that are unconstitutional, yet they persist in doing so over and over.
At some point, these elected activists need to be held accountable when they violate the constitutional rights of gun owners -- especially when the same schemes have been ruled unconstitutional over and over. Unfortunately, any monetary awards to the plaintiffs would come from the pockets of tax payers, not the individuals passing these illegal laws.