Sorry---the grammar nazi in me has to provide a "teaching moment" on this one. I hear this frequently in my workplace and it has become a personal pet peeve.
Precedence = status established in order of importance or urgency (e.g. The medics treated them in order of precedence according to their injuries.)
Precedent = An example that is used to justify similar occurrences at a later time (e.g. Having discovered a similar case in the past, the prosecution team used this precedent to support their argument)