Don't know fore sure about Delta but the Europe 1/Trema releases were all legal.
When the Thelonious Monk, Roland Kirk, Charles Mingus et al estates went after Esoldun for their releases of INA material (and won), they did not touch the Europe 1 deal.
Too bad that the Europe 1 jazz archives remain dormant nowadays. Still wish someone would dig out the 1959 Lester Young broadcast from the Europe 1 studio off the Champs-Elysées avenue: