Exclusive Presidential Power to Select Diplomatic Agents

Charlie Savage reported yesterday that OLC has issued an opinion (available here) concluding that Congress exercised its spending power in an unconstitutional manner when it purported to bar the White House's Office of Science and Technology Policy from using appropriated funds to plan or participate in bilateral contacts with China or Chinese-0wned companies.  Specifically, OLC concluded that the spending constraint unconstitutionally infringed the Presidents "exclusive power to conduct diplomacy," including discretion in selecting his diplomatic agents. This strikes me as correct.  An interesting tidbit about the memo, though: it does not mention that classic presidential foreign-relations authority Curtiss-Wright, nor does it invoke Jackson's tripartite framework from Steel Seizures (it does cite Frankfurter in Steel Seizures, though only for the proposition that historical practice endorses the view that executive power includes primary responsibility for foreign affairs).