If the true aim is to disarm the poor, it makes sense that the police and the military should be exempted from the law. By their very nature, laws to stop inexpensive firearms cannot stop such firearms from reaching criminals. Inexpensive arms are inexpensive because they are easy and cheap to manufacture. They can be manufactured in a criminal's basement. It isn't difficult.
Firearms are just pieces of metal, stamped or molded.
It doesn't take a rocket scientist. But if it takes a criminal, then only criminals will have these arms. The law-abiding, as usual, will abide by the law. And these arms will be all the more useful because the law-abiding have been disarmed. Criminals will have free play in the streets and homes of the poor.