Yes, over sixty patents have been issued for “tax planning methods.” You discover (or contrive?) a loophole, then patent its use. Subsequent taxpayers (or tax avoiders) who might happen on the same idea are obligated to contact you and arrange to license your innovation. This is not what the Framers had in mind when they empowered Congress
To promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries
Cong. Rick Boucher introduced a bill a couple of years ago to limit the benefits patent holders could obtain for such patents (summarized here(doc) with full text here(pdf)). A message today from Vaughn Henry implies that this has been reintroduced.