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.
The pigs love to stick their thumb on the scale so that they can hit you with a more severe charge, so I'm sure they'd love it if your shrooms weigh 10x because of the water weight.
