From the General Instruction of the Roman Missal (2002). Please note the emphasized passage:
The priest then takes the paten or ciborium and goes to the communicants, who, as a rule, approach in a procession.
The faithful are not permitted to take the consecrated bread or the sacred chalice by themselves and, still less, to hand them from one to another. The norm for reception of holy Communion in the dioceses of the United States is standing. Communicants should not be denied holy Communion because they kneel. Rather, such instances should be addressed pastorally, by providing the faithful with proper catechesis on the reasons for this norm.
When receiving holy Communion, the communicant bows his or her head before the Sacrament as a gesture of reverence and receives the body of the Lord from the minister. The consecrated host may be received either on the tongue or in the hand, at the discretion of each communicant. When holy Communion is received under both kinds, the sign of reverence is also made before receiving the precious blood
(GIRM 160; emphasis added).
The universal norm for reception of Communion is on the tongue. In those countries that have received a dispensation (among them is the United States), Communion may be received in the hand. As the GIRM outlines, where Communion in the hand is allowed, the decision for the means of reception belongs to the communicant. The only exception is when the minister of Communion dips the host into the precious blood before offering it to the communicant. In that case, Communion must be received on the tongue.
Norms for the Distribution and Reception of Holy Communion Under Both Kinds**
by the United States Conference of Catholic Bishops (USCCB)