If you miss half a day, they cannot dock you UNLESS you were on protected medical leave under FMLA. That is the ONLY legal way an exempt employee (which is the correct term - salary is only a pay method and does not denote your status) can have their pay docked for a partial day's absence, particularly in California.
However, if you miss a full day or more, you CAN have your pay docked depending on the circumstances. Essentially, if YOU take a day off, for non-illness related reasons, they can dock you. If THEY tell you not to come in, they have to pay you.
There is one exception to this. If you have been suspended for a major safety violation, you can be docked. Starting August 23, if you are suspended for ANY disciplinary reason, you can be docked.