TBM 700/TBM 850
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 3.5
Confusion; Distraction; Situational Awareness
Conflict Airborne Conflict; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Human Factors; Procedure
Aircraft X was on the JANNY3 arrival.  Aircraft Y was level at FL200.  I was stepping Aircraft X down reference Aircraft Y.  Aircraft X was pulling out in front of Aircraft Y and had been cleared to FL210.  The pilot questioned the clearance which I restated and which he read back. Separation was lost when Aircraft X continued to descend.  I instructed him to climb and maintain FL210 and told him that he'd only been cleared to FL210.  I apologized to him twice for the confusion associated with the new procedures we have at ZLA.  Later; when I walked up to the Operations Manager in Charge; he was taking the phone call from the pilot.  The pilot didn't understand that the altitude assignment overrode the Descend Via procedure.In this case; it appears pilots are not being adequately trained in Descend Via procedures.  Somehow; they are not getting the information they need. I don't know who is responsible for the training of corporate pilots but they have been failed by the system.  This is without question a very serious safety issue.  As a controller who loves what I do and the pilots I do it for; it is heartbreaking to have a pilot deviation in my sector.  I would much rather be the one who made the mistake. The video and audio recording of this incident proved that; as the OMIC told me; I 'did everything right.'  There is absolutely no comfort in that.
ZLA Center Controller reported that two aircraft were being stepped down and the higher aircraft descended to an altitude they were not given; leading to a loss of separation.