The correct answer is Anti-Gridlock Law.
The Anti-Gridlock of 1987 governs the entry of a vehicle into an intersection or a railroad. A driver is only allowed to enter an intersection if there is enough space to get all the way through one. Even if the light is green the driver may have to wait if the traffic ahead of him is blocking the passage.
Anti-Gridlock Laws are not unique to California but apply in most large cities in the USA. The 'Do not block intersection' sign is usually a clear indication of that law.
Drivers not obeying this law are punished with fines or penalties.
