From a David Weber post to Baen's Bar Snerkers Only dated July 26, 2009:

Source of the Eridani Edict

    The Eridani edict in its current, formalized incarnation is a product of the Solarian League. That doesn't mean it wouldn't exist as a pragmatic "If we do this, we get hammered" form even without the League. As things stand at this moment, the League is the self-appointed policeman in charge of enforcing the notion of reprisal as punishment, but most non-insane star nations are going to be aware that if they do this kind of thing, no matter how well they think they've concealed their tracks, word is likely to get around, and the consequences will be Something They Don't like™.