The group of all
automorphisms of a chain Ω forms a lattice-ordered group A (Ω) under the pointwise
order. Let G be an l-subgroup of A (Ω) which is o-2-transitive, i.e., for any
β < γ and σ < τ, there exists g ∈ G such that βg = σ and γg = τ. It is
shown that G is a complete subgroup of A (Ω) if and only if G is completely
distributive if and only if G contains an element ≠1 of bounded support.
There is a discussion of the pathological groups in which these conditions are
absent.