Constitution comes before following orders for a very important reason
When someone joins United States military, they swear an oath to defend the constitution because without that rule of law, we have no freedom or security worth protecting.
General Keith Alexander should be court martialed and imprisoned for his actions.
"I, ___, do solemnly swear (or affirm) that I will support and defend the Constitution of the United States against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; and that I will obey the orders of the President of the United States and the orders of the officers appointed over me, according to regulations and the Uniform Code of Military Justice. So help me God."*
Over at least the past decade, Alexander has repeatedly broken the law either with or without the consent of two presidents. Instead of being punished he has been repeatedly promoted. An officer or soldier actually has a duty to ignore orders when they are illegal.
Not only has Alexander spied on Americans and collected information without warrants, he has lied under oath to Congress. This is the sort of behavior that leads to tyranny. With friends like this, who needs enemies?