Advocates of net neutrality, which is under active assault by the conservative chairman of the Federal Communications Commission, have been pointing to a vivid example of how abandoning the principle will allow internet providers to manipulate their offerings at the expense of consumers.

The example comes from Portugal, where the rule change advocated by FCC Chairman Ajit Pai is in full cry. It provides an instructive look at how internet service providers can steer users to favored websites and services, including their own. And it’s a warning about the consequences of Pai’s proposal.