The Bureau of Alcohol, Tobacco, Firearms and Explosives or more commonly the ATF has announced an update to Form 4473, the background check form. All Federal firearms licensees or FFLs will have to switch to the form on Jan. 16, 2017. The previous form, drafted in 2012, will no longer be accepted from that point on.
Anyone buying from or transferring a firearm through an FFL will have to fill out this updated form. The bulk of the changes to the form are small clarifications to how the background check questions are phrased but one change stands out noticeably.
Question 11.e asks if the person filling out the background check is “An unlawful user of, or addicted to, marijuana” among other controlled substances. It has a new warning that points out that marijuana use remains “Unlawful under Federal law regardless of whether it has been legalized or decriminalized for medicinal or recreational purposes” under state law.
This change reflects the ATF’s longstanding position that local laws don’t supersede the federal laws the ATF is tasked to interpret and enforce. As long as there are federal laws that criminalize the consumption or possession of marijuana it will be illegal for cannabis users to purchase firearms.

In case there was any confusion — agree with it or not, says the ATF, right on the 4473. (Photo: ATF)
It’s not a legally gray area even if the enforcement of these and similar laws can sometimes be difficult or even impossible in these municipalities. This supports recent case law as well.
Recently the 9th U.S. Circuit Court of Appeals ruled that federal laws that prohibit drug users from purchasing firearms still apply to marijuana users, even in states where marijuana use has been decriminalized for medical or recreational use.
See Also: Ninth Circuit Appeals Court Says No to Guns for Medical Marijuana Users
Other changes to the form include a new format for filling out names for the background check process. Anyone with no middle name will have to mark the form NMN and anyone with only a middle initial must mark their initial with IO for initial only. Additionally, anyone with a name suffix like junior or senior will be required to include that information as well.
The new form uses the stricter term “sex” instead of “gender” for the purposes of identification and includes language detailing federal laws and definitions to help people correctly fill out the form. The updated form also includes instructions on how to proceed if a transfer is initially denied then overturned.
Legal experts at Orchid Advisors have a detailed list of the changes which number in the dozens. “If you have additional questions regarding the revised Form 4473, please contact your local ATF office. A listing may be found online (https://www.atf.gov/contact/atf-field-divisions).”
The new forms can be found online on the ATF website.

linky

I don't believe the ATF is ever going to be allowed to just ignore federal law and at the moment pot use is still a violation of federal law. This is why I don't believe the states legalizing pot will be the end all do all people are believing it to be, state laws do not supersede federal laws.

So what does the FFL do if that “An unlawful user of, or addicted to, marijuana” box is checked? Not allow the transfer?

Chad, AFAIK, if you check any box yes where the "correct" answer is no, then the clerk has no choice but to NOT proceed with the sell or transfer.

So if I went to Colorado and ate a "cookie", is that a yes or a no?? I don't know.

According to the State of Colorado, no. According to ATF, yes.

Question. Is a non FFL legal private gun owner selling or gifting a firearm to another owner, bound to the same guidelines and restictions as stated on form 4473?

It is given a responsible private seller would adhere to the 4473 transfer requirements. The question regards possible legal consequences.

Not sure of federal statutes, but here is the state statute that covers it. Intentionally and knowingly are pretty clear, but reckless could be a little more problematic for you depending on the situation. I tend to err on the side of caution where this is concerned.

Sec. 46.06. UNLAWFUL TRANSFER OF CERTAIN WEAPONS. (a) A person commits an offense if the person:
(1) sells, rents, leases, loans, or gives a handgun to any person knowing that the person to whom the handgun is to be delivered intends to use it unlawfully or in the commission of an unlawful act;
(2) intentionally or knowingly sells, rents, leases, or gives or offers to sell, rent, lease, or give to any child younger than 18 years any firearm, club, or illegal knife;
(3) intentionally, knowingly, or recklessly sells a firearm or ammunition for a firearm to any person who is intoxicated;
(4) knowingly sells a firearm or ammunition for a firearm to any person who has been convicted of a felony before the fifth anniversary of the later of the following dates:
(A) the person's release from confinement following conviction of the felony; or
(B) the person's release from supervision under community supervision, parole, or mandatory supervision following conviction of the felony;
(5) sells, rents, leases, loans, or gives a handgun to any person knowing that an active protective order is directed to the person to whom the handgun is to be delivered; or
(6) knowingly purchases, rents, leases, or receives as a loan or gift from another a handgun while an active protective order is directed to the actor.
(b) In this section:
(1) "Intoxicated" means substantial impairment of mental or physical capacity resulting from introduction of any substance into the body.
(2) "Active protective order" means a protective order issued under Title 4, Family Code, that is in effect. The term does not include a temporary protective order issued before the court holds a hearing on the matter.
(c) It is an affirmative defense to prosecution under Subsection (a)(2) that the transfer was to a minor whose parent or the person having legal custody of the minor had given written permission for the sale or, if the transfer was other than a sale, the parent or person having legal custody had given effective consent.
(d) An offense under this section is a Class A misdemeanor, except that an offense under Subsection (a)(2) is a state jail felony if the weapon that is the subject of the offense is a handgun.

Thanks.