Adron P. Brainerd (Brainerd) appeals the dismissal of his diversity action which was dismissed under the doctrine of res judicata. In his pro se brief, Brainerd does not brief the issue of whether his second action was barred by the doctrine of res judicata. Although pro se litigants are afforded liberal construction, even pro se litigants must brief arguments in order to preserve them. See Yohey v. Collins, 985 F.2d 222, 224-225 (5th Cir. 1993). Thus, the issue is deemed abandoned. Id. at 225. Because Brainerd has failed to argue the only issue arguably on appeal, the appeal is frivolous and must be DISMISSED as such. See 5th Cir. R. 42.2. Brainerd is WARNED that the filing of future frivolous appeals may result in sanctions.