The Novus Ordo Mass can be said in accordance with Sacrosanctum Concilium, 36.
I assume you refer to the Extraordinary Form of the Roman Rite, I answer that provided they can pronounce and grasp an understanding of basic Latin, then any priest of the Latin rite may say the Extraordinary Form of the Roman Rite in accordance with the Rubrics of the *Missale Romanum * of Bl. John XXIII, published in 1962.
As was recently provided for in the 2007 Apostolic Letter of Pope Benedict,
Summorum Pontificum. Article 2 states:
“In Masses celebrated without the people, each Catholic priest of the Latin rite, whether secular or regular, may use the Roman Missal published by Bl. Pope John XXIII in 1962, or the Roman Missal promulgated by Pope Paul VI in 1970, and may do so on any day with the exception of the Easter Triduum.”
Article 5, § 4: “Priests who use the Missal of Bl. John XXIII must be qualified to do so and not juridically impeded.”
You can read the Motu Proprio
here.
I think the FSSP do not train up their seminarians with the Ordinary (“Novus Ordo”) form, - preferring the tridentine rite, but I could be mistaken.