"The treatise found that he was perfectly within his rights to use them"

This quote is referring to a legal writing that was conducted to determine whether a person was within their rights to utilize something. The treatise found that the person was certainly within their rights to utilize whatever it was they were attempting to utilize. This might suggest that the individual was legally enabled to use something, such as a piece of residential or commercial property, a service, or a product. It could also mean that the person was enabled to do something, such as take a specific action or make a certain choice. In either case, the treatise found that the person was legally enabled to do whatever it was they were attempting to do. This quote is a testament to the importance of legal treatises and the power of the law in identifying what is and is not enabled.