Google Sued for Allegedly Refusing Anti-China Ad at Wired News covers a lawsuit filed against Google after it refused to carry ads from activist Christopher Langdon protesting against the Chinese government.
You'll find the lawsuit here. I skimmed it very, very quickly. The key part is this:
Google's rejection of all three of my ads denied my rights of free speech and to petition the government for a redress of grievances.
In other words, Langdon is claiming constructional protection to say what he wants on Google. It's not going to happen. Google has no requirement to print what he wants or carry his ads any more than a newspaper might. The public forum/public property argument he makes won't hold up, I'd say.
The courts will decide, of course. I suspect he'll lose, but it will certainly focus renewed attention on Google's ad policies that he dislikes.