This should be an easy answer but it isn't. Night vision and thermal devices are generally legal to own in the United States, except for in the state of California. Currently, California has laws against the possession of attachment and similar devices that are used with firearms and allows the user to visually determine and locate the presence of objects during the nighttime. Certain conditions will allow you to use a night vision device legally.
The law in California regarding the possession and use of night vision devices can be a little tricky. But here's a quick little breakdown:
- Active IR scope with magnification
- Passive IR scope with magnification and IR illuminator
- Active and Passive IR scope with no magnification
- Passive IR scope with magnification
- Passive IR scope with no magnification and an IR illuminator
- Active IR goggles with and without magnification
- Passive IR goggles with magnification
- Passive IR goggles with magnification and an IR illuminator
- Passive IR goggles without magnification and an IR illuminator
However, as long as your NVD uses a passive light, that is legal. In other words, as long as there is no infrared light source, it is legal to own and possess your NVD. It is unlawful to use or possess infrared technology for night-vision devices, and this includes binoculars and scopes. And, any type of night vision device that is attached to a firearm or not and uses light-amplifying circuits that are powered by batteries or electives are also illegal.
If you would like to have a look at the California Penal Code Section 486, you can check it out here. If you're interested in learning about the Fishing and Hunting Regulations in California, the California Department of Fish and Wildlife should be your best resource for you to double-check if your equipment is legal.