Some states permit in-house counsel to practice in the state so long as they only represent their corporate employer and register with the state. Registration is not free or hassle-free. However, in Opinion No. 15-01 (May 2015), the Illinois State Bar concluded that in-house counsel who limited his practice to patent practice did not need to register.
This issue comes up in many forms. For example, what can a patent agent do? The USPTO has defined what is, and is not, practice before the office and those definitions should be carefully consulted. But this Illinois opinion is a bit of good news to in-house counsel in my law school’s state.