from Fr. Zuhlsdorf's blog:
[...] citation of His Holiness Summorum Pontificum:
Art. 5, § 1. In parishes, where there is continuously present a group of the faithful attached to the previous liturgical tradition, let the pastor willingly receive their petitions that Mass be celebrated according to the Rite of the Missale Romanum issued in 1962. Let him see to it that the good of these faithful be harmoniously brought into accord with the ordinary pastoral care of the parish, under the governance of the Bishop according to canon 392, by avoiding discord and by fostering the unity of the whole Church. (copied)