the goal is to prevent US citizens from 3d printing guns,
Are you so silly that you think the US government has an interest in keeping guns out of the hands of US citizens?
The US has the highest per capita gun ownership in the world. Back in 2013, there was a gun for every man, woman and child in the US, and now certainly even more than that. The US government doesn't care about your guns. In fact, they know you are statistically more likely to kill yourself with that gun than you are someone else.
Do you see Second Amendment activists using guns against the government anywhere in the US? Do you think you're little gun worries the US government in any way, shape or form?
You dumb sonofabitch, your guns are just another way the government controls you. It's population control by another name and the argument is between you and "them libruls", not between you and the government, and the government knows this. As long as you're busy marching around open-carrying and fighting with liberals over gun control, you're not aware of just how controlled you are. As long as the "Second Amendment" is a big issue in elections, they know you're taking your eye off of what's really going on. You think you're a big winner when you march down to the local gun shop and spend your disability money on guns, and the government is laughing at you.