Unlike the Venezuelans, there is a level of difficulty here that he has been returned to his home country. The Venezuelans may have a better case here.
Nevertheless, the "you put him there, you get him back" makes an awful lot of sense.
in the first instance, this is an exercise of executive power over immigration that is not an inherent power, only delegated by Congress. It is not an initio either a foreign affairs or national security matter. That is something arbitrarily engrafted onto it by Trump. And even then, he acts pursuant to an act of Congress, the Alien Enemies Act.
At some point, though, the agreement or treaty with ES to take unlawful immigrants comes into play, and some of that may be covered by executive privilege. In a criminal prosecution of a citizen, that privilege would yield to the rights of the accused (US v. Nixon). Here, in a civil or quasi-criminal proceeding against a non-citizen, I'm not so sure. One would have to think that the agreement itself would have to come into evidence, if not the negotiations that led to it. And one might think that such an agreement might constitute a treaty, invalid without the advice and consent of the Senate.
It's a messy thing.