A few random links:
http://www.newmediarights.org/guide/legal/Video_Games_law_Copyright_Trademark_Intellectual_Property
http://lawofthegame.blogspot.co.uk/2007/06/copyright-what-every-gamer-developer.html
And a general search link:
I have an idea listed for my YouTube channel to cover this very topic…
EDIT
OH and my opinion… forgot to add, Tetris is a closely guarded IP, so unless you renamed it entirely and added a few differences, and I must say they have added a lot of variation to the IP, then as long as it is not a Nintendo IP, you might be ok, but to be honest, just put it out there as Open Source and move on to something more original… or find a novel way to re-implement a similar gameplay mechanic…
I have done this with my upcoming game, so it can totally be done.