Q: I seem to recall reading somewhere that any saint in the Roman Martyrology may be celebrated liturgically, if the table of precedence allows it, and if there is pastoral benefit. 1) Is this correct? 2) If so, may I celebrate the Mass on February 14 in honor of St. Valentine?
A: GIRM 354 and 355 answer this no.
A priest follows the calendar for obligatory memorials, such as Saints Cyril and Methodius on February 14.
Saints from the martyrology may be chosen on simple weekdays or on optional memorials.