I need to change the rear brake assemblies. after I took off both rims and drums I can not turn the axles by hand. is this normal or should I be able to just grab the lugs and freely turn the wheel?

Well around here only dumb question is the question not asked. But most likely you have the car in park which is the reason you cannot turn the axle's try that put it in neutral and see what happen but chalk your front wheels for the car will not role.