I'm not positive but I think the only state that has laws against bringing in plant materials is California. I'm sure there are others here that will know more about this subject though.

I've mailed cuttings, not plants with native soil on their roots, but cuttings to many states in the Continental US for over two and a half decades. I've received cuttings from many states in that time, too. I have mailed cuttings to several areas of Canada; seeds to Canada and Australia; budwood to Belgium and The Netherlands, and I've never had to have anything other than a Customs Form from the Post Office for shipments out of the country. I've never had any issues sending or receiving cuttings from any of the 48 continuous United States.

If you send cuttings to Canada, you send them as "wood samples", no value. The same for bud wood overseas. For seeds to Australia, I simply listed them as "Rosa hybrida seeds (cross or variety name).

I simply use Priority Mail, usually Flat Rate, and no one has ever interfered. Kim

There are restrictions on sending plant material into California, Arizona, Oregon, and Washington. Each of these states have laws in place to protect their agricultural industry. California's laws are the strictest. Most of their laws are to protect against soil-borne cooties (like Japanese beetles from infected states). The Virginia Department of Agriculture site has exact regulations on what can and cannot be shipped from Virginia.

Shipments INTO Virginia must be inspected and certified to be free of brown snails. Every state is different.

Budwood, without soil, poses fewer risks ... but do you want to be the one to whom a disease is traced if you inadvertently spread it to a place where it doesn't exist? The rules are in place for everyone's protection.