California's law against carrying a concealed weapon, Penal Code 25400 PC, makes it a crime for most members of the general public to carry a concealed firearm on their person or in a vehicle.
There is an exception to California's concealed carry law for people who have obtained a concealed weapons permit. In order to get this permit, you need to meet certain requirements, including a showing of "good cause."
A recent federal lawsuit, Peruta v. San Diego, challenged these laws, arguing that they violate the Second Amendment to the U.S. Constitution (which protects the right to bear arms). The law's opponents focused on the "good cause" requirement for a concealed weapons permit, arguing that it created too high a barrier for people seeking such a permit. In 2014, a 3-judge panel of the Ninth Circuit Court of Appeals agreed and held that California's concealed carry laws are unconstitutional.
But the case was appealed to the entire Ninth Circuit. And several days ago that court, sitting "en banc," held that in fact PC 25400 and California's concealed weapons permit requirements are NOT unconstitutional.
The Ninth Circuit concluded that the Second Amendment does not extend to concealed firearms--and that there is, therefore, no constitutional right to carry concealed weapons.
There is a chance this case will be appealed to the United States Supreme Court, which may reach a different conclusion. For now, California's concealed weapons laws are here to stay.