Here an interesting bulletin out of the UK from last year summarizing the state of the law regarding space debris.
http://www.parliament.uk/documents/documents/upload/postpn355.pdfMostly it's concerned with things going "bump" while _in_ space but the general thrust of international law right now is: If you throw it up you are responsible for it until it comes back down. All satellite launches are insured for the whole life of the thing -- or so this bulletin claims.
Cosmic debris, e.i. meteors, are considered an Acts of God. The Almighty is probably well indemnified but filling out those forms on stone tablets is a drag....