On Friday, the new law raising the age to purchase tobacco products and e-cigarettes to 21 went into effect . The new restriction will only lead to more confusion about what we consider the age of legal adulthood and what rights “adults” are entitled to under the law.

For a long time, 18 was considered the line of demarcation in our society when a young person became an adult. Now, things increasingly aren’t so clear. The years between 18 and 21 are defined by an odd hodgepodge of rules and regulations, the rights of adulthood only partially bestowed by those legally recognized as adults but, culturally, often still treated as children.

This inconsistency isn't tenable over the long run. Such illogical lawmaking breeds contempt for the rule of law and encourages its flouting. Governments can right this wrong by either rolling back restrictions to granting 18-year-olds the full rights and responsibilities of adulthood or by biting the bullet and pushing back the legal age of adulthood to 21.

The current state of affairs is illogical.

Right now, at age 18, you gain the right to vote and are trusted with full participation in our electoral system. So, too, 18-year-olds are considered “adult” enough to enlist in the military, get married without parental permission, consent to sex, and so on. But our laws, in typical nanny-state fashion, also tell those same young people they can’t be trusted with the freedom to smoke cigarettes, use e-cigarettes, or drink alcohol (or not) as all other adults. In many states, too, the Second Amendment right to self-defense is arbitrarily stripped from legal adults under 21.

This inconsistency is impossible to justify. Surely anyone deemed trustworthy enough to risk his or her life in conflict overseas and have full sexual autonomy should also have legal decision-making power over their own body when it comes to mint-flavored Juul pods.

Yet the solution isn’t quite as simple as just rolling back everything to age 18. While the inconsistency is puzzling, there are compelling reasons to keep some of these age restrictions at 21.

For instance, the human brain doesn’t finish developing until age 25. Additionally, as life expectancy, educational attainment, and the age at which people choose to get married have all increased, it’s only natural that our period of youth has extended until 21. There are simply far fewer 19-year-olds living and working on their own today, with many of that age still at least somewhat dependent on their parents. Why should we consider them legal adults?

Moreover, keeping the alcohol age at 21 is effectively all that keeps 14-year-old high schoolers from having unrestricted access to hard liquor through their 18-year-old friends in the senior class. The policy raising the e-cigarette age to 21 at least offers a more sensible way than ill-advised flavor bans to address the rise of vaping in schools.

These restrictions on the rights of adults are simultaneously utterly inconsistent and fairly well warranted. But philosophically, morally, and just sensibly, it only makes sense to keep these restrictions in place if we raise the age of adulthood to 21. The state has no right to deny legal adults decision-making power over such relatively frivolous issues, compared to what is otherwise currently demanded of and granted to 18-year-olds.

Changing the age would be no small feat, either. At least as far as the federal voting age is concerned, a change would require a constitutional amendment. Raising the age for military enlistment poses challenges, as well. For one, it would most certainly require “grandfathering” of those currently enlisted who are under 21, and we would also need to expand options for those aged 18 to 21 who choose not to enroll in college. More apprenticeships and job training programs could be an answer.

It won’t be easy, but we must make this change if we are to keep the current regime of age-based restrictions in place. The status quo is not just logically inconsistent but is philosophically unjust in the way it limits the rights of legal adults.