If you want to be a firm lawyer, it would be better to have a firm job your 1L summer (and you'd wind up with an extra $30k+). But most of the time the study abroad sign-up date is after most employers hire, so you could look at it as a back-up option.
I agree: use it as a back up. We have a summer program abroad, but a couple of my profs told me that it pretty much looks like you took a vacation instead of working your 1L summer. I'm sure some employers will see value in it though; especially given your interest in international law.