UKColumn states "This is problematic for Trump because a declaration, although it would not normally have the force of law, in this case the declaration was added as an addendum to a treaty, and the treaty was used for the sale of the Danish West Indies (now the Virgin Islands) to the US. The declaration went through the full ratification process.....So, although under normal circumstances, a unilateral declaration by the US would not be binding, in this case it is binding because it was part of that treaty that was ratified.....and is therefore constitutional. It is domestic law we are talking about here, not international law, and it is much much harder for Trump to breach that."