I see a lot of comments using U.S. rules, the op stated CAA, which indicates out of the U.S.. The simple best answer is checking the UAS rules for his country regarding flying over someone else's property, photographing someone else's property. And check for local ordinances for photographing from a UAS. There may be local privacy laws regarding surveillance, voyeurism, peeping toms, etc. There are some places here in the U.S. that have these laws and prosecute UAS operators for taking pictures of someone's private homes.
Since this is a legal case, check with your attorney to see if you can get a warrant authorizing the taking of the photos to protect youself.