National Conference of Catholic Bishops, General Decree Concerning Clerical Dress, 1 November 1999.
The National Conference of Catholic Bishops, in accord with the prescriptions of c. 284, hereby decrees that without prejudice to the provisions of c. 288, clerics are to dress in conformity with their sacred calling.
In liturgical rites, clerics shall wear the vesture prescribed in the proper liturgical books. Outside liturgical functions, a black suit and Roman collar are the usual attire for priests. The use of the cassock is at the discretion of the cleric.
In the case of religious clerics, the determination of their proper institutes or societies are to be observed with regard to wearing the religious habit.
As President of the National Conference of Catholic Bishops, I hereby decree that the effective date of this decree for all the Latin Rite dioceses in the United States will be December 1, 1999.
Given at the offices of the National Conference of Catholic Bishops in Washington, DC, on November 1, 1999.
Most Reverend Joseph A. Fiorenza
Bishop of GalvestonHouston
Reverend Monsignor Dennis M. Schnurr
Code of Canon Law Annotated (Montreal: Wilson & Lafleur Limitée, 2004): 1791. www.usccb.org/norms