Limited Power of Attorney if you are a RIA that doesn’t custody trading for direct clients.  If you are a RR with a B/D, then it is covered in the Discretionary Adivosry Contract.  If you are a RIA acting as a subadvisor on a single contract SMA platform, then it is handled through the Advisory contract between the sponsor and you.  If you are a RIA acting as an Investment Advisor on a dual contract SMA platform, then it is handled through the Advisory contract between you and the client.  If you are a RR that hasn’t be approved for discretionary accounts with the BD, then it is handled through a non-compliant pact between you and the client.
Any questions?
If you are a RIA and have a FULL Power of Attorney of a client’s account, then that would deem you to have ‘custody’ under the new custody rules.
PM me if you need more.