  The objects known as anomalous X-ray pulsars and soft gamma repeaters are
commonly identified with magnetars, neutron stars with ultrastrong magnetic
fields. The rotational history of these objects has, so far, revealed no
evidence of free precession. At the same time these objects do not generally
appear to have magnetic axes nearly parallel or orthogonal to their spin axes.
In this paper we show that the combination of these two observations, together
with simple rigid-body dynamics, leads to non-trivial predictions about the
interior properties of magnetars: either (i) elastic stresses in magnetar
crusts are close to the theoretical upper limit above which the crustal matter
yields or (ii) there is a "pinned" superfluid component in the magnetar
interior. As a potentially observable consequence of these ideas we point out
that, in the case of no pinned superfluidity, magnetars of stronger magnetic
field strength than those currently observed would have to be nearly
aligned/orthogonal rotators.
