Minimum age for sales and transfers: California prohibits any person, corporation or firm from selling a handgun to anyone under age 21, and from selling, loaning, or transferring any firearm to a “minor.” This prohibition does not apply in certain scenarios, including the sale of a handgun that is an “antique firearm” to a person at least 18 years of age, and the transfer or loan of a long gun to a minor by the minor’s parent or legal guardian. The California Family Code defines the term “minor” to mean an individual who is under 18 years of age.
Minimum age for possession: California law prohibits minors from possessing a handgun. Exceptions to this prohibition include situations where a parent or legal guardian is present or has consented to the possession. In addition, minors may, with the consent of a parent or guardian, possess handguns when engaged in certain recreational sports, including, but not limited to, competitive shooting; agricultural, ranching, or hunting activities; and any motion picture, television, or video production, or entertainment or theatrical events, the nature of which involves the use of a firearm.
There is no minimum age to possess rifles and shotguns in California, although federal age restrictions still apply.
Law Center To Prevent Gun Violence
(a) Unlawful sexual intercourse is an act of sexual intercourse accomplished with a person who is not the spouse of the perpetrator, if the person is a minor. For the purposes of this section, a “minor” is a person under the age of 18 years and an “adult” is a person who is at least 18 years of age.
So the "tabacco age" is 21, the age of consent is 18, the legal drinking age in the US is 21, the driving age starts with a learners permit at 15 - criminal responsibility in California starts with 14.
A child can be tried for selling tabacco to a minor, but can not consent to buying the tabacco.
But it doesn't stop here, back to the Penal Code:
(c) Any person who engages in an act of unlawful sexual intercourse with a minor who is more than three years younger than the perpetrator is guilty of either a misdemeanor or a felony, and shall be punished by imprisonment in a county jail not exceeding one year, or by imprisonment pursuant to subdivision (h) of Section 1170.
Notice something? Picture the case of a 17 year-old having sex with a 14 year-old. You think that's wrong because under 18 you couldn't possibly know the consequences are and couldn't possibly consent? Fair enough. What the law in California says though is that you can't know because you're not ready, but you are totally ready to be punished if you do it anyway.
Tabacco at 21 is really the smallest problem here.