  We derive and discuss the constraints induced by Poincare' invariance on the
form of the heavy-quark potential up to order 1/m^2. We present two
derivations: one uses general arguments directly based on the Poincare' algebra
and the other follows from an explicit calculation on the expression of the
potential in terms of Wilson loops. We confirm relations from the literature,
but also clarify the origin of a long-standing false statement pointed out
recently.
