[DrScump]

But CA law also says you can't enter an intersection without having clearance to vacate it. In other words, if the cross street itself is backed up such that its traffic backs up or into that intersection and prevents you clearing the intersection as you complete the turn, you violate the "anti gridlock" law.

[WillPostForFood]

That's not relevant to this situation. Waiting for oncoming to traffic to clear, then turning while the light is red is legal, and orthogonal to whether "there is sufficient space on the other side of the intersection". If there isn't sufficient space to turn, whether the light is green, red, or yellow, then you can't turn and are violating the anti gridlock law. If you entered the intersection before it turn red, and there is space to turn, you can turn on green, yellow, or after it turns red.

[joecool1029]

Most jurisdictions do not consider it blocking the box if you enter the intersection to turn and it turns red after. They consider it blocking the box if you enter with the intention of going straight while it is not clear to do so.

This is the case for NY state, see VTL 1175: http://www.safeny.ny.gov/rowa-vt.htm

[DrScump]

CA Vehicle Code 22526(a): "Notwithstanding any official traffic control signal indication to proceed, a driver of a vehicle shall not enter an intersection or marked crosswalk unless there is sufficient space on the other side of the intersection or marked crosswalk to accommodate the vehicle driven without obstructing the through passage of vehicles from either side."

https://leginfo.legislature.ca.gov/faces/codes_displaySectio...

[romwell]

This does not seem to be relevant to the situation here (waiting for the oncoming traffic to clear): usually, there's plenty of space to turn into, but one has to yield to oncoming traffic before occupying that space.