Kicking the habit

I had a fight/discussion recently with a friend on the status of priests from religious orders who are ordained diocesan bishops.  I said that I thought they ought not to continue wearing the habit of their order.

At the time I couldn't find the evidence but I have today come upon the Instruction of the Secretariat of State, Ut sive sollicite, on the dress, titles, and coats-of-arms of Cardinals, Bishops, and lesser Prelates (31st March, 1969).


Section 17 says:

Episcopi ex Ordinibus vel Congregationibus religiosis delecti utentur veste talari violacei coloris, veste talari cum vel sine torulo, globulis, ocellis ac subsuto rubini coloris, haud secus ac ceteri Episcopi.

Bishops chosen from religious Orders or Congregations will use the purple cassock, and the cassock with or without red trimming, buttons, buttonholes, and lining, just as other Bishops.

That seems pretty definitive to me.