Instantaneous Interactions in Standard Model

Instantaneous interactions in Standard Model are derived by the resolution of the Gauss constraints in inertial reference frames defined as irreducible representations of the Poincare group. The relativistic covariant and gauge-invariant S-matrix is constructed with taking into account instantaneous interactions. Physical effects formed by the instantaneous interactions are discussed, including the enhancement in the kaon --> pion transition probability and the nonleptonic and semileptonic kaon decays. The low-energy relations between these decay probability amplitudes and meson form factors are established. Exploiting these relations we estimate possible parameters of the differential K \to \pi e^+ e^- decay rate in the NA48/2 CERN experiment.