Nevada law is what counts. Cannabis consumption is for private use only. It is illegal to smoke in public, on federal land or in a vehicle without risking a fine.
There are some hotels that allow tobacco smoke, but most will not permit marijuana use because of concerns regarding conflicting federal law. This is especially true of casinos that work hard to meet gaming regulations, which makes them less likely to want to "gamble" with federal marijuana law.
Although there has been some discussion about opening a few marijuana resorts on Las Vegas Boulevard in the future, it's always best to keep a low profile when consuming cannabis in Nevada.
Those caught violating public consumption laws in Nevada will be charged with a misdemeanor which is punishable by up to six months in jail, a fine of up to $1,000 or both. The ruling judge may assign community service in addition to or in lieu of both jail time and fines.