I am not sure how familiar you are with the details of this Awalaki case, but the son was not hit at the same time as his father, rather two weeks later while dining with some teenage friends. There is no indication that the son or any of his friends were terrorists when they were hit by the drone strike. The son left the Yemeni capital and went into the mountains looking for his father; he left before it was all over the news and apparently didn't know that his dad was already dead.
As for Awlaki. himself, if you are a lawyer or a legal fan, this one is a real trip.
Anwar Awalaki's father had requested that the ACLU represent his son's legal interests. But once they slapped that terrorist label on Awlaki, the ACLU had to request "a license" from the Treasury Department to represent Awlaki lest they be considered "associated with terror" themselves. Treasury ultimately denied them the license, so piece of crap or not, Awlaki was allowed no legal remedy once he was put on that "kill list".
I'm no fan of scimitars -- but neither am I a fan of jackboots.
2. The Treasury Department should absolutely NOT be in the business of "licensing" lawyers in any event, no matter what the excuse. We managed to have the Stalinist Rosenbergs who conspired to turn nuclear weapons secrets over to the soviets represented very well by first rate and independent trial lawyers (likely communists as well but that is irrelevant) on the Rosenbergs' way to the electric chair without the republic collapsing. See Louis Nizer's The Implosion Conspiracy. And Stalin was generally conceded to be a bit more of a threat than Al Qaeda and its Islamonutcase allies.
2. Separation of powers: Lawyers are all officers of the judicial branch of government. If lawyers need to be "licensed" by the executive branch of government before they dare represent the popularly damned in courts, then will the executive next decide that it must license citizens before they can be elected to Congress? Before, as criminal defendants, they can plead not guilty and contest charges? If Timothy Geithner, Treasury Secretary in Obamaville, is belatedly indicted for income tax evasion, will his department claim a right to "license" prosecutors to prosecute him? Time for the ACLU to grow a pair and either put up or shut up. They don't need a Treasury Department "license" to represent the ACLU itself in an action against Comrade Obozo, his Treasury Department, and anyone else who would like to claim that lawyers representing clients can be, on that basis alone, be regarded as co-conspirators. Temporary and permanent injunction, temporary and permanent mandamus, declaratory judgment and maybe even an action in quo warranto alleging that even considering much less granting or denying such licenses by the Treasury Department (no less) exceeds any legitimate power of the department or any executive department and is therefore ultra vires. It wouldn't have taken three seconds for the ACLU to seek such remedies against Nixon or Reagan if they had tried such arrogant extension of executive power.
3. Anwar Awlaki's kid: If he is not even collateral damage (as he must not be if murdered in some dining joint with his teenaged friends while blissfully unaware of dad's previous demise). The kid was an American citizen and the government seems to have had no excuse to assassinate him. This distinguishes his death from that of Osama bin Laden's on both counts. Due process was owed to the kid and not to bin Laden (who should have been bathed in pig blood on film before burial.) I would also imagine that any statute of limitations on legal actions to seek damages to redress the kid's death would be suspended while the executive branch tries to intimidate lawyers as officers of the judiciary from bringing such actions.
4. For actual terrorists convicted after full due process, slow death by scimitar would seem an appropriate substitute punishment instead of utterly unspectacular and unsatisfying death by injection. If necessary, delay the punishment during any period during which the convict is providing useful intel for us to kill his/her colleagues in terrorist crime. Also scimitars will generally trump jackboots and should be legally deployed whenever jackboots have been against those deploying the jackboots.
5. I am a recovering attorney and generally no fan of the court system but it DOES have its uses AND its OBLIGATIONS. My dissatisfactions with the judicial branch are no excuse for that branch to shirk its obligations. If we have had to make believe for nearly forty years that women have a "right" to hire abortionists to murder the unborn just because SCOTUS says so, then the judiciary should step up to the plate and show its imperial sweep in matters that count and are actually its responsibility like enforcing due process of law and protecting its officers from illegal intimidation by the Treasury Department or any other executive bureaucracy.
Note however that the criminal cleric al Awlaki AND his son were killed AFTER initiation of the lawsuit. The judiciary has an obligation to prove its own gonads by recognizing that the airstrikes against two American citizens (however reprehensible excuses for human beings) are a direct challenge to judicial authority. What would the judiciary do if an apparently state statute authorized governor of a state ordered state police and militia to militarily attack an abortion mill and kill all the perps of the abortions (right down to the receptionists and the janitors and the security guards) on the perfectly sensible theory that they are engaged in a conspiracy in serial homicide and present a clear and present danger of continuing their abortions, Roe vs. Wade or no Roe vs. Wade? Without modification of Roe vs. Wade, the judiciary would go nuclear. Due process is quite explicitly guaranteed in the Constitution unlike "reproductive rights" or anti-reproductive "rights" for that matter.