The general resource kit for answering a question like this would be the reading list for a course on political philosophy.

http://www.iep.utm.edu/polphil/

http://people.brandeis.edu/~teuber/polphil.html

Of course there are more specific resources.

http://plato.stanford.edu/entries/freedom-speech/

http://plato.stanford.edu/entries/pornography-censorship/

http://hope.journ.wwu.edu/tpilgrim/j190/week1Meiklejohn.html

http://www.iep.utm.edu/ockham/#SH8c