It comes down to whether Trump’s order was lawful, he said. If Trump was trying to prevent Vindman from sharing sensitive information, it could be. If he was trying to prevent testimony, period, it’s not.

The Military Whistleblower Protection Act prohibits government officials from interfering with a member of the military in communicating with Congress or an inspector general. Adding to the complexity is that the president gets to determine what is and isn’t classified.

“If the president were to order the lieutenant colonel not to testify, that would not be a lawful order,” Timmons said. “However, it gets tricky, because you have to obey orders unless it is manifestly unlawful. It’s not clear if such an order would be manifestly unlawful if the president is using his executive authority to prohibit the communication of information that the executive branch determines to be classified, sensitive, top secret, not to be disclosed to anyone without prior authorization.”