One of those seed exchange libraries got shut down a little bit ago. It was held in the local library, and people would pick up or donate seeds as they wished. It was stopped and the patrons were told that it was illegal because nobody had spent thousands of dollars testing every variety for purity, germination, and so forth.
I am not sure if it is a Federal law or state laws, but in many areas at least it really is illegal to simply share seeds!
People still do it, of course. The laws are there, though thankfully they are not necessarily enforced.
Yet. Wait a bit!