How can we say"devolución en caliente" in an immigration context?

express deportations

Everywhere I've looked it is literally translated as a "hot return." Some who use that designation explain that the "process" originates in Spain.

It's basically the immediate denial of entry to those who try to seek asylum or try to illegally enter a country at places other than where expected (like when someone climbs over a wall and is caught in the act). These people are summarily denied access to the country without regard given to their request for asylum, asylum they may have been granted had they entered by the gate where such requests are formally heard through the process of law.

I'm not sure that even "express" carries a strong enough connotation of speed. I'd suggest instant deportation.

I found involuntary return on an American webpage of immigration