  In this paper we discuss a constructive approach to check whether a constant
Hamiltonian is Yang-Baxter integrable. We then apply our method to long-range
interactions and find the Lax operator and $R$-matrix of the two-loop SU(2)
sector in N=4 SYM. We show that all known integrable long-range deformations of
the 6-vertex models of this type can be obtained from a Lax operator and an
$R$-matrix. Finally we discuss what happens at higher loops and highlight some
general structures that these models seem to exhibit.
