When we've set up local defense force militias, either in Iraq or Afghanistan, critics here have opposed it worrying that they'd become little warlord militias that would contribute to violence rather than fight insurgents. While their worry about possible outcomes is justified, local defense forces properly trained and regulated are a key factor in generating the numbers you need to protect/control populations at an affordable cost.
Face it, even if you could recruit and afford it, it wouldn't make sense to have SEAL Team 6-level troops for every security task from storming an outpost behind enemy lines to manning a traffic circle check point.
But you have to watch militias and retrain them when they stray or disband them when no longer needed to avoid them becoming a threat. Indeed, early in the Iraq War I counted Shia militias in the government column because they did carry out needed self-defense missions against Sunni Arab terrorists. But by 2006, they were just Iranian-backed death squads that were purely part of the threat. So they can go bad.
But Assad shows what critics of local defense forces really worry about: militias whose purpose upon establishment is just to kill:
The Syrian government is reportedly using local militias known as Popular Committees to commit mass killings which are at times sectarian in nature, U.N. human rights investigators said on Monday.
But of course, that reflects the difference between why we set up local defense forces--protecting people from insurgents and terrorists--and the Syrian government' objectives which the militias complement rather than undermine:
"Indiscriminate and widespread shelling, the regular bombardment of cities, mass killing and the deliberate firing on civilian targets have come to characterize the daily lives of civilians in Syria," Pinheiro said.
What you are fighting to achieve really matters. Assad's militias are doing exactly what he intended them to do. They're just another means to kill and terrorize civilians.