  A new paradox in superluminal signaling is presented. In contrast to the
Tolman paradox with tachyon exchange between two parties, the new paradox
appears already in a one-way signaling, even without creating the time loop. As
shown in the article, a one-way superluminal signaling would, by swapping cause
and effect, violate the factual invariance of some related physical processes.
This produces a universal ban on any kind of superluminal signals, which is
much stronger than the Tolman paradox. Even though relativity embraces
superluminal motions as such, thus making the world symmetric with respect to
the invariant speed barrier, the ineptness of all such motions for superluminal
signaling makes the symmetry incomplete.
  Key words: superluminal signaling, tachyons, the Tolman paradox
