Convoy of what? The PCA only says federal troops can't be used for law enforcement - not relief work.
"Posse Comitatus act generally prohibits U.S. military personnel from direct participation in law enforcement activities. Some of those law enforcement activities would include interdicting vehicles, vessels, and aircraft; conducting surveillance, searches, pursuit and seizures; or making arrests on behalf of civilian law enforcement authorities."
Mostly Humvees. In all probility they were unarmed. No BFV's Towing covered trailers, maybe had morters, don't know about that.
barbra ann