This is a topic about which rubrics are silent and history
may provide little clear-cut guidance!
Many suggest that it is appropriate for those to be baptized
to receive ashes on Ash Wednesday as a sign of metanoia and of a
desire to be united to Christ. Thus, they argue, it is just as appropriate
for any of the "elect" to be chosen to have a foot washed, as
a sign of willingness to allow Christ to be the one who will continue
to cleanse them from sin. On the other hand, there are ritual
moments when it seems particularly appropriate to make a distinction
between the baptized and the "elect." For example, since
those to be baptized will symbolically receive the "light of Christ"
for the first time only after their Baptism (RCIA, #230), some
dioceses have explicitly legislated that that the "elect" do not carry
candles at the beginning of the Easter Vigil.
Should the foot-washing be considered more like receiving
ashes or more like holding a candle at the Easter Vigil?
The inclusion of the "Mandatum" (foot-washing) rite in the
Mass of the Lord's Supper in the Roman rite is relatively recent and
is not universally practiced in the Church in other ritual families.
For example, in the Ambrosian Rite of Milan, Italy, the "mandatum"
is, in fact, prohibited during Mass on Holy Thursday!
The current Holy Thursday rite seems to have originated in
monastic communities (wherein everyone was already baptized)
and then slowly was included in cathedral and parochial settings.
In the 1570 Missal, however, the rite took place after Mass and the
stripping of the altar and was restricted to clergy. The corresponding
Ceremonial of Bishops (of 1600) mentions an alternative
practice, that of bishops washing the feet of paupers. In this
era, however, adult catechumens were virtually non-existent in
most of Europe and so the question of washing the feet of nonbaptized
would not arise. It was not until the interim reforms of
Holy Week in 1956 that the foot-washing rite was officially
permitted during Mass.
What may seem odd is that a fourth-century
reference to a rite of foot-washing occurs, not in the
context of Holy Thursday rites, but rather in the
description of the initiation rites. Saint Ambrose of
Milan mentions that after neophytes were baptized and confirmed,
they had their feet washed. There is speculation that in
some Christian communities highly influenced by the Gospel of
John, post-baptismal foot-washing may have been a regular practice
because of John 13:10. Here, in response to Peter's plea that
Jesus wash his hands and head, Jesus says, "Whoever has bathed
has no need except to have his feet washed, for he is clean all
over." If one interprets the reference to "bathing" as a reference to
Baptism, then this verse could be interpreted as suggesting that
foot-washing is to be done only for those already baptized.
If one sees foot-washing as having a significant baptismal
symbolism (as do the holy water fonts at the entrances to
churches), and if participating in the rite (or taking holy water
with one's fingertips) is seen as a symbolic renewal of Baptism,
then one can legitimately wonder how appropriate it is for someone
not yet baptized to participate in the rite (or make the Sign of
the Cross with holy water).
Too often, our modern, technological culture limits an action
or object to having just one meaning. The tradition of the Church,
however, is that liturgical objects and actions have multiple meanings.
The foot-washing is not only a call to service and humility,
but also a symbol of union with Christ through Baptism (see John
13:8, "Unless I wash you, you will have no inheritance with me").
Taking all these aspects into account, it seems best to me to
recommend that the "elect" not be among those who participate
in the foot-washing on Holy Thursday.