If someone is on the phone and I walk up and ask "do you consent to this conversation being recorded" and they agree, can it be used in court?

Louisiana is a one-party consent state to recording conversations. This means that in Louisiana, you are legally allowed to record a conversation if you are a contributor to the recording. There is not even a necessity that you make a statement asking for their consent to record. All that is required is that you are a party to the recording and can be heard on the tape. Recordings of conversations that you are a part of are also admissible as evidence in civil and criminal proceedings so long as the recording meets certain criteria: (1) That the recording device was capable of taking the conversation now offered in evidence; (2) That the operator of the device was competent to operate the device; (3) That the recording is authentic and correct; (4) That changes, additions or deletions have not been made in the recording; (5) That the recording had been preserved in a manner that is shown to the court; (6) That the speakers are identified; and (7) That the conversation elicited was made voluntarily and in good faith, without any kind of inducement. Though I do not know the specifics of the restraining order you have in place, threats made to a protected party are a violation of the protective order and in most Louisiana courts it is common for the order to state that the retrained party be prohibited from making harassing phone calls. Recordings of those threats can very likely result in the Court finding that they are in violation of the restraining order.