Yes, an enlisted member can file a complaint under Article 138, UCMJ, if they believe they are the victim of Unlawful Command Influence (UCI) during their court-martial, but it is not the most immediate or effective remedy. An Article 138 complaint is a formal process where a soldier complains to a higher commander about a wrong committed by their own commanding officer. While UCI is a wrong, the Article 138 process is administrative and can be slow. A more direct remedy is available within the court-martial itself.
The immediate and proper course of action is for the military defense attorney to file a motion directly with the military judge presiding over the court-martial. The motion would allege UCI and would ask the judge to investigate the matter and provide a remedy. The judge has broad authority to deal with UCI. They can order a hearing to take testimony about the alleged influence. If they find that UCI has occurred, they can grant a variety of remedies to cure the prejudice.
These remedies can include excluding tainted evidence, providing special instructions to the panel members to disregard the influence, or, in the most egregious cases, dismissing the charges entirely. This judicial remedy is much faster and more effective than the administrative Article 138 process. While an Article 138 complaint can be filed in parallel to hold the commander accountable administratively, the primary battle against UCI during a trial is fought directly in front of the military judge.