Learn how to make gunpowder from such items as dead cats, whiskey, your living room ceiling, manure and maple syrup with simple hand tools and techniques that have been used for centuries. This is a practical and safe approach to making the oldest propellant/explosive known. For information purposes only.
Some of what he says is difficult, especially considering the rabbit holes you have to engage for some of the chemical fixes. However, the chemistry and safety warnings are solid. Having been a "garage" chemist for fireworks and black powders while being mentored by a true blue educated working chemist, I can verify it will work. Just very much follow his advice on safety. Please, this shit can kill or worse, maime.
Oh, and yes, it's perfectly legal in the proper use.
Even felons can use black powder firearms and should, if reformed of the crime that got them sent up originally. The Second Amendment means all citizens.