It's legal in the US (in all but three states I believe), because the spores do not contain psylocin/psylocybin. Once you start to grow them though, you could be charged with possession of a controlled substance.

Don't let that stop you though GP! It's a fun project and very satisfying to see your mushrooms finally sprouting up after a month or two of work. The risk of getting caught is low, and even if you somehow did, it would probably still be worth the penalty if they have a positive effect on your wife's headaches!