The new laws passed in 2018 restricting short-term rentals in the City of Los Angeles went into effect on July 1, 2019.
It is now known as the Home-Sharing Ordinance, and is being administered and enforced by the Dept of City Planning.
They have all of the information online regarding how to register your home [ if it is owner-occupied & is your principal residence],or how to report any homeowners who violate the restrictions. The website is:
planning.home-sharing@lacity.org or planning.lacity.org/HomeSharingOrdinance
You can also reach the Dept by phone at 213-202-544 or call their 24/7 hotline 213/ 267-7788