Yes, very large hassle. You would be importing a firearm into the US. Several things you will need to do, including determine IF that rifle CAN be legally imported into the US.
As a minimum you will need an approved ATF from 6 http://www.atf.gov/forms/download/atf-f-5330-3a.pdf
to get the rifle into the US. Many people hire an import firm, such as Simpson LTD to do the paperwork. Ain't cheap.