In mostly any state there is a certain amount of ambiguity concerning the legality of magic mushrooms. But in the United States, laboratory grade mushroom studies are regulated in almost all the states, with only a few exceptions.
In other words, it is not illegal to sell the spores, but illegal to do that in order to grow mushrooms from them, due to the fact that the spores do not contain psilocybin, but the fully-developed mushrooms do. And despite the fact that mushrooms can be found in nature, too, a laboratory grade spore syringe is obviously the better option for researchers who intend on studying them in a full-equipped, legitimate laboratory.
And lab grade mushrooms or laboratory grade mushroom spores, to be more precise, are certainly kept under the best conditions possible for making the research an easy task. Spores can get contaminated very easily. And those who intend to study them should avoid buying low quality spores. Some people may use mushroom spores for study at home, if certain specific requirements are fulfilled, such as: having a sterile location for making the inoculation, having an incubation room and a microscopy one for doing the actual research. At any rate, since the effect of these shrooms is still studied, scientific research is generally encouraged.