But this tech isn't required by law, is it? You can legally make your own printer without a $50 bill detector.

Correct. And even if this bill passes you can build your own printer from common parts or drive across state lines to the nearest Micro Center. It’s useless posturing regulation for the sake of looking tough.

The proposed legislation is about the sale and distribution of 3d printers. You could build your own 3d printer legally without the detector software.