Justin Martin describes a procedure that enables the running of PS2 games purchased in the US on a PlayStation 2 purchased in Europe (this hack might also work the other way round).

When I moved from Ireland to the US, I brought along my PS2; I hadn’t had it that long, and I wasn’t going to leave it behind (despite many offers to give it a good home ;).

Of course, Sony include plenty of trade-restrictive features in the PS2; European games won’t play on a US PS2, and vice versa.