Last year, the EU court ruled that publishers and vendors cannot legally prohibit the re-selling of downloaded games and licenses. The ruling explicitly mentioned "licenses", as that had been the "workaround" that Valve/Steam had used to circumvent similar rulings before.
Now the German VZBV (consumer protection central) seems to make its move against Valve/Steam in an effort to force a re-selling option for Steam-bought games:http://www.cinemablend.com/games/Valve-Steam-Policies-Get-Challenged-Court-Gamers-Could-Resale-Their-Games-Says-VZBV-57648.html
I think this is an important step. Most things you buy you can also sell again, because you do own them. This doesn't have to be bad for Valve, actually, because there would be nothing that prevents them from taking a fee for managing the transactions, so the revenue generated by such fees would possibly off-set the loss from decreasing sales. It would be more problematic for publishers, who were probably already happy that the second-hand market had been crashed (for the PC) by digital distribution.
If Valve loses a possible lawsuit, it would only affect the EU, since there are no similar rulings from US courts, as far as I'm aware.