Part (b) is related to war time. Part (a) is not.
With regard to part (a) and a possible death penalty, it is not inconceivable to me that Bannon could have been conspiring with others to share war plans, communications intelligence, or "other major element of defense strategy," etc. with the Russians.
There has been a death penalty prosecution for espionage (since the Rosenbergs) -- against Brian Regan. (The prosecutor sought the death penalty but the jury imposed a life sentence without parole.) And there is an ongoing prosecution in Virginia for espionage that could involve the death penalty. (See below).
But there has never been an administration like the current one. I don't put anything past Bannon or most of the people in it. I don't give any of them the benefit of the doubt.
https://www.law.cornell.edu/uscode/text/18/794
18 USC 174
(a) Whoever, with intent or reason to believe that it is to be used to the injury of the United States or to the advantage of a foreign nation, communicates, delivers, or transmits, or attempts to communicate, deliver, or transmit, to any foreign government, or to any faction or party or military or naval force within a foreign country, whether recognized or unrecognized by the United States, or to any representative, officer, agent, employee, subject, or citizen thereof, either directly or indirectly, any document, writing, code book, signal book, sketch, photograph, photographic negative, blueprint, plan, map, model, note, instrument, appliance, or information relating to the national defense, shall be punished by death or by imprisonment for any term of years or for life, except that the sentence of death shall not be imposed unless the jury or, if there is no jury, the court, further finds that the offense resulted in the identification by a foreign power (as defined in section 101(a) of the Foreign Intelligence Surveillance Act of 1978) of an individual acting as an agent of the United States and consequently in the death of that individual, or directly concerned nuclear weaponry, military spacecraft or satellites, early warning systems, or other means of defense or retaliation against large-scale attack; war plans; communications intelligence or cryptographic information; or any other major weapons system or major element of defense strategy.
(b) Whoever, in time of war, with intent that the same shall be communicated to the enemy, collects, records, publishes, or communicates, or attempts to elicit any information with respect to the movement, numbers, description, condition, or disposition of any of the Armed Forces, ships, aircraft, or war materials of the United States, or with respect to the plans or conduct, or supposed plans or conduct of any naval or military operations, or with respect to any works or measures undertaken for or connected with, or intended for the fortification or defense of any place, or any other information relating to the public defense, which might be useful to the enemy, shall be punished by death or by imprisonment for any term of years or for life.
(c) If two or more persons conspire to violate this section, and one or more of such persons do any act to effect the object of the conspiracy, each of the parties to such conspiracy shall be subject to the punishment provided for the offense which is the object of such conspiracy.
(d)
http://abcnews.go.com/WNT/story?id=130183
A federal judge on Thursday rejected attempts by defense lawyers to prevent the government from seeking the death penalty for accused spy Brian Regan.
Regan, a retired Air Force sergeant, is charged with trying to sell military satellite secrets to Iraq, Libya and China. He is a former intelligence analyst who worked at the National Reconnaissance Office, which runs the nation's spy satellites.
The government says Regan took 800 pages of classified information and may have buried even more. He allegedly offered secret data to Iraq and Libya for $13 million. He was arrested a year ago as he tried to board a flight to Switzerland.
In April, federal prosecutors filed court documents declaring their intention to seek the death penalty. It is the first time in decades that the government has sought the death penalty in an espionage case. No U.S. citizen has been executed for spying since Julius and Ethel Rosenberg in the 1950s.
http://www.foxnews.com/us/2017/06/22/virginia-man-charged-with-espionage-for-giving-top-secret-documents-to-china.html
A Virginia man has been charged with espionage for transmitting top-secret documents to Chinese officials.
Kevin Patrick Mallory, 60, was arrested Thursday at his home in Leesburg, Virginia, and appeared in U.S. District Court in Alexandria.
Mallory, a self-employed consultant and Army veteran, was charged with gathering or delivering defense information to aid a foreign government and for making material false statements under the federal Espionage Act.
SNIP
He could face life in prison and the charges, if certain conditions are met, could make Mallory eligible for the death penalty, according to prosecutor John Gibbs.
= new reply since forum marked as read
... there's an eight letter word mixed in there and a damn acronym. 
