I don’t think this is a helpful comparison. A citizen in the service of an enemy engaged in war against his country does not enjoy the protections of an arbitrary citizen. We can rightly argue whether that theory wholly fits the facts of al-Awlaki, but it’s a very, very long bridge from that case to Sotomayor’s hypo
Not really—once you've crossed that bridge it's a short hop to the government arguing that the political rival was a terrorist who needed to be killed.
Due process is about validating the government's claims before allowing it to kill someone.