Q. Is a woman assisting at the Extraordinary Form of the Roman Rite obliged to wear a head covering?
A. No. This obligation was codified in the 1917 Code of Canon Law as Canon 1262. The 1917 Code, however, has been abrogated in toto. Since the obligation was a disciplinary norm that had been codified in the Code, its omission from the revised code, together with the abrogation of the 1917 Code, means that the prior norm is of no effect.
The instruction Universae Ecclesiae, issued by the Pontifical Commission Ecclesia Dei on the implementation of Benedict XVI’s motu proprio Summorum Pontificum, makes two pertinent points:
27. With regard to the disciplinary norms connected to celebration, the ecclesiastical discipline contained in the Code of Canon Law of 1983 applies.
28. Furthermore, by virtue of its character of special law, within its own area, the Motu Proprio Summorum Pontificum derogates from those provisions of law, connected with the sacred Rites, promulgated from 1962 onwards and incompatible with the rubrics of the liturgical books in effect in 1962.
Thus, rubrics and matters of law set forth in the liturgical books themselves are governed by the liturgical book in use: for the Mass celebrated according to the Extraordinary Form of the Roman Rite, the Missale Romanum as promulgated by St. John XXIII on June 23, 1962, and the accompanying Codex Rubricarum promulgated in 1960. Laws and norms from other sources, however, are not revived: these matters remain governed by the ecclesiastical law otherwise in force today, even in the context of the celebration of the Extraordinary Form.
 1983 CIC c. 6 § 1(1).
 Instruction on the Apostolic Letter Summorum Pontificum of His Holiness Benedict XVI Given Motu Proprio, 103 A.A.S. 413 (Pontifical Commission Ecclesia Dei, April 30, 2011), available in translation at http://tinyurl.com/3b7khct.