The Kiss of Peace Is Optional
Is the kiss of peace an optional part of the Mass—i.e., may the priest remove it without violating any Church law?
Yes, the sign of peace is optional. The General Instruction of the Roman Missal (154) states that the celebrant asks the congregation to exchange the sign of peace "when appropriate" (GIRM 154). When the GIRM describes a Mass with a deacon (181), it repeats this language by stating the deacon asks the congregation to exchange the sign of peace "if it is appropriate."
It is therefore at the discretion of the celebrant whether it is appropriate at a particular Mass to exchange the sign of peace.