The binding comprises a pair of pistons (7, 8) extending under the boot and each stressed by a spring (14, 15). The arms of a sole clamp (2, 3) act on these pistons. The pistons are connected together by a linking means (20), and the binding comprises means (24, 25) for controlling the linking means, capable of occupying a first position, in which the pistons are secured by the linking means, and a second position in which one of the pistons is able to move on its own, at least over a certain travel common to the two pistons. The control means (24, 25) are controlled magnetically by the boot so as to obtain a binding with asymmetrical release resistance.