States (and other Bar regulators) have long tried to protect certain segments of the Bar from competition coming from other segments of the Bar. For instance, states have tried to prohibit the kinds of advertising used by personal-injury lawyers. Greg Beck of Public Citizen has done great work (go, for instance, here and here) convincing courts to strike down some of these restrictions on free-speech grounds.
Here's another variation: A New York statute requires its Bar members who reside outside the state to maintain an office in the state. That increases costs for out-of-state lawyers -- for instance, someone who practices out of her home in Hoboken, New Jersey, but serves New York clients -- for no legitimate reason. Last year, a federal district court held that statute unconstitutional under the Privileges and Immunities Clause of Article IV of the Constitution. We recently filed this brief to the Second Circuit on behalf of more than 20 non-resident members of the New York Bar explaining why the lower court's decision should be affirmed.