No, a finding of not guilty (an acquittal) by a court-martial panel does not legally bar a command from initiating a subsequent administrative action, such as a separation board, for the same underlying conduct. This is permissible because the two proceedings have different standards of proof. A court-martial acquittal means the government failed to prove the misconduct “beyond a reasonable doubt,” the highest legal standard. An administrative board uses the much lower “preponderance of the evidence” standard, meaning “more likely than not.”
Because the administrative standard is easier to meet, a command can legally take the same evidence that was insufficient for a criminal conviction and try to use it to secure an administrative discharge. This is often called the “second bite at the apple.” The command will argue that while the evidence didn’t meet the high criminal standard, it is still sufficient to show that the misconduct more likely than not occurred and that the service member is unsuitable for continued service.
However, the acquittal is the defense attorney’s most powerful piece of evidence at the administrative board. The attorney will argue forcefully to the board members that it is fundamentally unjust to separate a service member for conduct of which they have been fully acquitted by a formal court-martial. They will contend that disregarding the acquittal undermines the integrity of the military justice system. While not a legal bar, this is an extremely persuasive moral and logical argument that often convinces a board to vote for retention.