From GWE's page on seed buying:
"Many, many growers order seeds online every day, and to this day there has never been a report of someone in the USA getting in legal trouble for simply ordering cannabis seeds online. You can check me on that! In fact, American citizens have been ordering seeds overseas via mail order from Amsterdam since at least the 1970s, and even though it's been over 40 years there hasn't been a case of an American getting in legal trouble simply for ordering cannabis seeds online through the mail!
An American citizen won't get in legal trouble for ordering cannabis seeds online from outside the country.However, because of the (backwards) way U.S. federal laws work surrounding cannabis, you can get in a lot of legal trouble for selling or sending seeds from one place to another within the USA, even between legal states! That's why you never see long-term cannabis seed banks located in the U.S.
When marijuana seeds get caught by customs agents during shipping, the seeds get tossed and that's it. It doesn't matter what state you're in, or your local laws. That is simply the way our laws about customs work. On the flip side, you can get in a lot of trouble by sending seeds from one place to the other within the US (though this is still very, very rare)."