  In this paper we discuss how the Magueijo-Smolin Doubly Special Relativity
proposal may obtained from a singular Lagrangian action. The deformed
energy-momentum dispersion relation rises as a particular gauge, whose
covariance imposes the non-linear Lorentz group action. Moreover, the
additional invariant scale is present from the beginning as a coupling constant
to a gauge auxiliary variable. The geometrical meaning of the gauge fixing
procedure and its connection to the free relativistic particle are also
described.
