That ruling could potentially impact the widely popular National Do-Not-Call Registry, set to take effect October 1.
The DMA, one of the plaintiffs in the case, said it was "grateful" for the ruling. It said it also continues to support a national list for consumers, pointing to its own Telephone Preference service established in-house 18 years ago.
The DMA said it would work with its attorneys and the FTC and Federal Communications Commission in the next several days to evaluate the implications of Tuesday's decision.
Meanwhile, FTC Chairman Timothy Muris denounced the decision in a statement Wednesday, calling it incorrect and citing "clear legislative direction" from both Congress, which passed the ruling, and President Bush, who signed it.