Are Catholics not supposed to pray the St. Michael Prayer? I was looking up exorcism stuff on the Vatican website and stumbled across this from (then) Cardinal Ratzinger (now Pope Emeritus Benedict XVI)

From these prescriptions it follows that it is not even licit that the faithful use the formula of exorcism against Satan and the fallen angels, extracted from the one published by order of the Supreme Pontiff Leo XIII, and even less that they use the integral text of this exorcism. Bishops should take care to warn the faithful, if necessary, of this.
Letter to Ordinaries regarding norms on Exorcism

So does that mean that the St. Michael Prayer:

Glorious St. Michael the Archangel, defend us in battle, be our protection against the wickedness and snares of the Devil, and do thou o Prince of the Heavenly Host, by the power of God, cast into hell Satan and all the evil spirits who prowl about the Earth seeking the ruin of souls. Amen

I learned by heart this prayer some 15 years ago and say every time the creepy crawlies pound on my windows at 3 AM is verboten?
The faithful may recite the Prayer to St. Michael the Archangel freely.

The prohibition from Pope Leo XIII is against the faithful’s use of the rite of exorcism—in other words, the pope is prohibiting the faithful from attempting an exorcism themselves, as only a priest or bishop may do this.

As the Catechism of the Catholic Church, No. 1673, explains,


  The solemn exorcism, called “a major exorcism,” can be performed only by a priest [evidently, a bishop may perform it as well] and with the permission of the bishop. The priest must proceed with prudence, strictly observing the rules established by the Church. Exorcism is directed at the expulsion of demons or to the liberation from demonic possession through the spiritual authority which Jesus entrusted to his Church [emphasis added].


The Prayer to St. Michael, on the other hand, is a popular devotional prayer (at one time recited as a part of the so-called “low Mass”), which is never a problem to recite. (It is never a problem for people to ask for the intercession of the saints in protecting them from the influence of Satan.)

The similarity of the Prayer of St. Michael to the rite of solemn exorcism in use at the time does not itself make the devotional prayer illicit. In fact John Paul II recommended its popular use at least once in a 1994 Regina Coeli address.