In the 1941 case of Ex Parte Don Ascanio Colonna, the U.S. Supreme Court ruled on a matter involving international law and diplomatic immunity. The petitioner, Prince Don Ascanio Colonna, was an Italian diplomat who had been detained by American authorities for failing to comply with a subpoena from a New York court in relation to his divorce proceedings. He argued that as an accredited diplomat he enjoyed immunity from such legal processes under international law. However, the U.S government contended that since Italy had entered World War II against America's allies at this point in time (though not yet against America itself), any diplomatic privileges held by Italian diplomats were effectively suspended. The Supreme Court sided with Colonna and ordered his release based on two main points: firstly because there was no formal state of war between Italy and United States when he was arrested; secondly due to lack of evidence showing that President Roosevelt had officially declared all diplomatic relations with Italy severed or suspended prior to arrest date.

The dissenting opinion in the case of Ex Parte Don Ascanio Colonna, 1941 is not readily available. This Supreme Court case involved an Italian prince who was held for deportation on charges of moral turpitude. The majority ruled that he could be deported despite his claim to diplomatic immunity due to his status as a member of the former royal family of Italy. However, without access to specific documents or records from this time period, it's impossible to provide a summary of any dissenting opinions offered during this case.