Depending on your specific question, you will need to look at different parts of the Oregon Revised Statutes (ORS) or contact state regulatory or consumer agencies. Here are a few places to start your research (in no particular order):
1) Do a quick search for Oregon consumer law and car rentals. For example, Laura Gunderson at the Oregonian “Complaint Desk” and Brent Hunsberger at the Oregonian’s “It’s Only Money” column cover a lot of useful Oregon consumer-protection ground; they are worth reading. They are also the first to say whoops if they make a mistake or overlook something, so don’t stop there with your research. (These columns move around the Oregonian website, so you may need to use a search engine to find them.)