Roll a D20: if it's even he comes back, if it's less than 10 he mysteriously disappears.

I wouldn't even put the odds of him coming back at 50%

20: He gets brought back in good condition, 19-16: He is gonna get brought back in terrible condition, 15-11 he doesn't come back, 10-1 he is dead

Note that I said "even" and "less than ten". Even ignoring damage he's already suffered in the prison, the "good outcomes" are still only 30% (10, 12, 14, 16, 18, 20).

If you read the SCOTUS ruling, all it upholds from the lower courts decision is that the USG must 'facilitate', not 'effectuate' his release. AFAIK the Court doesn't have a way to order El Salvador to do so