When a cleric is found guilty of sexual abuse of a minor what canonical measures can be applied?

The canonical measures applied in dealing with a cleric found guilty of sexual abuse of a minor are generally of two kinds: 1) measures which completely restrict public ministry or at least exclude the cleric from any contact with minors. These measures can be reinforced with a penal precept; 2) ecclesiastical penalties, among which the most grave is the dismissal from the clerical state.

In some cases, at the request of the cleric himself, a dispensation from the obligations of the clerical state, including celibacy, can be given pro bono Ecclesiae.

Circular Letter, To Assist Episcopal Conferences In Developing Guidelines  For Dealing With Cases Of Sexual Abuses Of Minors Perpetrated By Clerics, Rome, from the Congregation for the Doctrine of the Faith, 3 May 2011

http://www.vatican.va/roman_curia/congregations/cfaith/documents/rc_con_cfaith_doc_20110503_abuso-minori_en.html

What is the prescription of a criminal action against perpetrator of crime against minors

The extension of the term of prescription of a criminal action to twenty years, maintaining the right of the Congregation for the Doctrine of the Faith to derogate from prescription on a case by case basis (art. 7).

A brief introduction to the modifications made in the Normae de gravioribus delictis, reserved to the Congregation for the Doctrine of the Faith, given at the Congregation for the Doctrine of the Faith, 21 May 2010.

http://www.vatican.va/resources/resources_rel-modifiche_en.html