I can't find them yet on the PTO's site, but here's one taste:
[A] registered patent agent is not authorized by his or her registration to practice before the Office to draw up a contract or to select contract forms for a client relating to a patent, such as an assignment or a license, if the state in which the agent resides or practices considers drafting contracts the practice of law. Assignments and licenses are the creation of state, not federal, statutory law. Although 35 U.S.C. 152, 202, 204 and 261 refer to assignment or licensure of patents or patent rights, assignments and licenses are forms of contracts, which are creatures of state, not federal law. Contracts are enforceable under state law. The authority to prepare contracts and provide advice regarding the terms to include in contracts is subject to the state law regarding who is authorized to practice law. In contrast, submission for recordation of assignments and licenses is a ministerial act that does not require legal training. It has been the long-standing position of the Office that a registered patent agent may prepare a patent assignment or license