Personal Use of Marijuana by Responsible Adults Act of 2009 - Prohibits the imposition of any penalty under an Act of Congress for the possession of marijuana for personal use or for the not-for-profit transfer between adults of marijuana for personal use. Deems the possession of 100 grams or less of marijuana as personal use (one ounce or less for a not-for-profit transfer between adults). Allows the imposition of a civil penalty under the Controlled Substances Act for the public use of marijuana if such penalty does not exceed $100.