As I wrote in 2007, post #6 of forums.catholic.com/showthread.php?t=134133 :
… Who can distribute the ashes on Ash Wednesday?
In the USA there is the following, from the Book of Blessings:
“1659 This rite may be celebrated by a priest or deacon who may be assisted by lay ministers in the distribution of the ashes. The blessing of the ashes, however, is reserved to a priest or deacon.” (The rite being referred to is the distribution of ashes outside of Mass). …
I am not aware of any permission for lay people to distribute ashes outside of the USA. In the USA there is no permission for lay people to distribute ashes in Mass.
The Roman Missal has “The priest then places ashes on those who come forward, saying to each: …” (page 77)
The Ceremonial of Bishops has:
“257 After the blessing, the appointed minister, a concelebrant or a deacon, places ashes on the bishop, as the bishop bows before him, and says, Turn away from sin and be faithful to the Gospel or Remember, man, you are dust and to dust you will return.
258 Then the bishop again puts on the mitre and, seated at the chair or standing, places ashes on the concelebrants, the ministers, and the faithful. The bishop may be assisted if necessary by some of the concelebrants or deacons.”