Las Vegas is known for legal regulation of human vices such as gambling and prostitution, so it comes as no surprise that recreational marijuana can now be enjoyed there with impunity, too. Toward the end of November 2016, Nevadans voted in the Regulation and Taxation of Marijuana Act. Cultivation, sales, possession, and use of marijuana became fully legal on January 1, 2017, albeit with some regulations. So, 1 oz. of weed will not cause anyone trouble, provided it is consumed privately. Yet is its derivative, cannabidiol (CBD) oil, legal in Nevada? [1,2]
Yes—according to state law, CBD oil is fully legal in Nevada, but only if it is extracted from industrial hemp. 
In this, Nevada law is perfectly aligned with federal law, which recently amended the Farm Bill to legalize industrial hemp.
The passage of the Hemp Act also saw this cannabis variety's removal from the country's Schedule I drug list. Hemp was clustered together with dangerous narcotics such as heroin and LSD—rather ridiculous, considering its harmlessness.
Marijuana is still seen as an illegal substance by the national government in the U.S., even though thousands—if not millions—of Americans are lobbying for a change of status. 
It is unclear whether CBD oil derived from marijuana is legal for use in the state of Nevada. To stay on the safe side, it would probably be better to stick with organically derived industrial hemp CBD oil.
Yet marijuana is known to greatly alleviate specific health conditions and to help with stress and anxiety if used responsibly. Fortunately, the law now allows for it, as said, but the regulations are still strict.
As mentioned, there are still rules and regulations in place regarding the use of recreational marijuana: 
Industrial hemp is defined, by law and the industry, as cannabis containing less than 0.3 percent tetrahydrocannabinol (THC).
THC, like CBD, is a chemical compound found in cannabis (called cannabinoids), and it has been proven to confer many health benefits. However, this cannabinoid is also causing the characteristic "high" or feelings of drugged euphoria weed users often hope to experience.
THC consumption is furthermore not entirely harmless, mostly when consumed in copious amounts and smoked like tobacco.
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Research has linked marijuana use to the following adverse effects: 
"Deficits in verbal learning, memory, and attention are the most consistently reported in heavy cannabis users but these have been variously related to duration of use, frequency of use, and cumulative dose of THC."
"These findings suggest that regular cannabis use may play a contributory causal role in bipolar disorders but the case is not yet compelling because these studies have not adequately controlled for confounding variables or ruled out reverse causation." (Reverse causation would mean the effects of marijuana use could be specific only to bipolar patients.)
So, despite marijuana's undeniable health properties, CBD may be the better compound to consider because it doesn't have any of the mentioned adverse effects.
Cannabidiol is generally considered safe for common use, as was reported by the World Health Organization in 2017. So far, it seems to have many indications for use, including treating the conditions listed above, but more and well-designed clinical study is necessary before it can be prescribed as such. 
In the meantime, consumers are left to their own devices, and it would probably be best to experiment.
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If it says the following on the label, the CBD oil is likely to be a good one.
1. ORGANIC: Organically grown hemp could be harmless because generally, organic farmers give commercial pesticides and chemical fertilizers a miss. This could mean fewer harmful chemicals in the crop. So far, not many studies have been conducted to determine the value of "organic" vs. "commercial" produce, but some research has shown that organically grown vegetables contain fewer contaminants, such as cadmium.
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2. CO2 EXTRACTION: CO2 is not the cheapest or easiest method of extracting CBD from hemp, but definitely the one that gives the purest end product.
3. LABORATORY TESTED: An ethical CBD oil producer will be unafraid to display a comprehensive lab report with their goods. Done by third-party laboratories, it should clearly list the contents of the oil.