I am against control in general because it limits creativity and innovation but I am not sure it is in everyone's interest to let weapons flow freely and without any possible limitation.
Some forms of DRM (XBOX360, for example) are tricky enough that it prevents a few people from bothering. Some forms of DRM are so obnoxious that they encourage people to pirate so they can make use of the content.
I can't see 3D-Printer-Controls being anything but cumbersome, easily circumvented, annoyances.
It's important to note that people who want guns can easily make bad guns already (or, with a bit of decent machinery, they can make good guns) or they can buy illegal guns.This is true even in the UK with our strict laws.
Controls on 3d printers may just shift the problem somewhere else. Scanners and photocopiers have controls about scanning / copying money. This makes it tricky to copy banknotes. A photocopied / laser printed bank note is a lousy forgery. It's really obviously fake. And criminals in England tend to forge £1 coins - about 2% of these coins are forged. Some of them are obvious slugs, coloured tin. Others are better quality - using the same planchets and thus they work in machines.