Now that you've aquired an illegal gun...

I live in California, which may have some of the strictest gun laws in the country.

Recently someone offered to sell me an AR15. The weapon was never used in a crime, the guy had purchased it pre-ban and had heard that I was contemplating moving out of the state.

So, in general, because I know that state laws vary, what would my options have been? Note: I didn’t purchase the gun, for a variety of reasons.

I find an old handgun in my mothers closet, so old it’s not registered. Someone dies and I inhereit firearms that are illegal in my state.

I find a clean, non-crime addled firearm in the woods.
How would I go about taking this found/salvaged firearm, and making it legally mine?

You also have to be eligible to even own a handgun in the first place, ie not be a criminal and register to own one. Dig around on this link:

http://caag.state.ca.us/firearms/index.html