IANAL. As I understand it the possession of dried shrooms is much less ambiguously illegal than fresh shrooms. It varies widely between states. In mine a rare prosecution for possession of fresh shrooms failed due to that ambiguity.
In most jurisdictions in the US, cultivated [psychoactive] mushrooms of any form are illegal. In some jurisdictions, spores are legal for microscopy only, but as soon as you cultivate them the organic mass becomes illegal.
https://www.inverse.com/article/7772-magic-mushrooms-are-leg...