Finsler spacetime in light of Segal's principle

ISIM(2) symmetry group of Cohen and Glashow's very special relativity is unstable with respect to small deformations of its underlying algebraic structure, and according to Segal's principle cannot be a true symmetry of nature. However, like special relativity, which is a very good description of nature, thanks to the smallness of the cosmological constant, which characterizes the deformation of the Poincaré group, the very special relativity can also be a very good approximation, thanks to the smallness of the dimensionless parameter characterizing the deformation of ISIM(2).