Today a judge in Virginia ruled that the mandate in Obama's health care law is unconstitutional. A Florida judge will hear a related case later this week. Aaron Carroll's analysis from before the ruling was announced:
[T]here’s no way this won’t be appealed to the Supreme Court. So the questions won’t be answered today. If the judges rule the mandate is unconstituitonal, that still won’t be the final word.
Even if they do rule it unconstitutional, it’s unlikely they will place an injunction on the law. The mandate doesn’t kick in until 2014, so there’s no reason to rush. Especially since the decision will be appealed.
Even if the mandate is ultimately found unconstitutional, that doesn’t mean the whole law will be thrown out. See this post.