The so called pomerium in Rome was the legal and religious boundary of the city of Rome proper. Even in antiquity the de facto urban area extended beyond those limits but it contained the inner city.
Certain special laws were in force in this area. Among those was a prohibition against bearing arms. So far so good - but does anyone know how it worked in practice?
Even in republican times Rome was large city. There wasn't much in terms of law enforcement as we know it. In general it isn't too hard to imagine how such a thing could work out. The rich and powerful, including the magistrates, had plenty of slaves at their disposal. One suspects that for the masses this meant a lot activity in the gray area between vigilantism and gang warfare. What is harder to imagine is such a society without weapons.
Was there an effective ban of privately owned weapons?
Was there a definition of "weapon" that left some leeway in practice?
How was the defense of the city affected? Was the pomerium completely inside the Servian Wall? (It's surprisingly hard to find good maps.)
A dictator's lictors were exempt from the ban. Did this extend to others under the command of dictator?