Google Public Policy Blog on Censorship as trade barrier:

Some forms of censorship are entirely justifiable: the worldwide prohibitions on child pornography and copyright infringement, for example.

Yes it is called justified here, but copyright is too seldom called censorship, regardless of how obvious that is.

Others, however, are overbroad and unwarranted. When a government blocks the entire YouTube service due to a handful of user-generated videos that violate local sensibilities –- despite our willingness to IP-block illegal videos from that country –- it affects us as a non-tariff trade barrier.

I have mixed feelings about this. On one hand, adding classes of trade barriers simply provides an excuse for “retaliatory” protectionism. Autonomous liberalization does the most good, and I suspect that’s as true of free speech as any other area. On the other hand, this is great to the extent free speech is actually promoted, either as intended or by crowding out pro-censorship (strong copyright) from the U.S. trade negotiation agenda.