[Non-Sequitur]

Read Title 10 USC 12301-12304. Reservists are, under most circumstances, activated under order of the President.

Obama himself isn't ordering this 'officer' to report, someone in his hierarchy is. I think this gentleman will find that that officer's order is valid.

[Joe 6-pack]

"Obama himself isn't ordering this 'officer' to report, someone in his hierarchy is."

Whoever in the officer's chain of command ordered him to report did so under the authority of the president.

It's that authority that's in question.