It's not actually possible to force someone to lobby for something. How could you be sure they were really trying? They could just hire really bad lobbyists or run really bad advertising, for instance.
Essentially, as part of the Master Settlement Agreement, the government just said, "You have to put X dollars into this independent anti-smoking group."
TheTruth.com uses web, print and television promote
its message.
As for forcing them to stop + lobby for it? You might even run into some Supreme Court issues, and they might challenge it on free speech grounds. It would be an uphill battle for something that might not even be enforceable (which is why I also said that it's not enough of a concession to make the merger a net public gain).