President Trump has spoken a bit more in recent days about his plans to end birthright citizenship, promising to sign an executive order that will “probably work its way up to the Supreme Court.” While his original statement to that effect got somewhat lost in the fervor surrounding the midterm election, it appears it wasn’t simply a ploy to influence those elections, and that he might actually pursue it as policy. Given that, it’s worth taking a serious look at the idea of birthright citizenship, and what we might lose with its elimination.

Set aside for a minute the fact that Trump almost certainly lacks the constitutional power to do what he’s proposing. The question of birthright citizenship, particularly for children of undocumented immigrants, is still by no means settled; as Peter Schuck and Rogers Smith argued recently in The Washington Post, there is an ambiguity in the 14th Amendment’s guarantee to birthright citizenship, which Congress could theoretically resolve in favor of the president. So the question is worth interrogating, regardless of the futility of Trump’s forthcoming order.

What exactly is birthright citizenship? Also called jus soli (“right of soil”), it’s the guarantee of citizenship to anyone born within the borders and subject to the jurisdiction of the United States (what exactly it means to be “subject to the jurisdiction” of the United States is the ambiguity mentioned earlier). The 14th Amendment was originally intended to establish and protect the citizenship of black Americans after the Civil War.

So should we favor or reject birthright citizenship? This is a tough question, so let’s start with a simpler, more fundamental one: Why should we care who becomes a citizen and how they do it?

For one, the gift of U.S. citizenship — or the withholding of that gift — has moral consequences. The rights and privileges afforded to U.S. citizens have the potential to make people’s lives much better, or even save them in some circumstances. Given this, it seems like the decision of who gets to be a citizen is a rather important one.

It follows that we should allocate citizenship in some non-arbitrary way, since we tend to think that morally important decisions should be made with good reason. Suppose I have a policy where I only donate to charities with a “J” in their name. We might think this is morally questionable, even if the net result is that I help some people, because I have seemingly refused to help certain people for no reason at all.

Of course, there’s more to citizenship than a simple gift of rights. It’s a sort of contract with one’s country and one’s fellow citizens, in which one agrees to abide by certain rules and fulfill certain obligations in exchange for the aforementioned rights and privileges. We might think that we should limit the pool of potential citizens to those people we can expect to abide by those rules and fulfill those obligations (or make a good-faith effort to do so).

With this framework in place, we can again ask: Does birthright citizenship, specifically for children of undocumented immigrants, allocate citizenship in a reasonable, non-arbitrary way?

In one sense, no! There are few things more arbitrary and outside of an individual’s control than the geographic location where they’re born. Surely, we can expect undocumented immigrants (and their children) to make a good-faith effort toward fulfilling the contract of citizenship, but it seems insane to say that one child gets to be a citizen and another does not based merely on which side of an imaginary line they happened to be born on.

Allowing neither child to be a citizen would be less arbitrary, but that’s surely a morally worse option — it would be like if I chose to fix my strange charity donation policy by refusing to give money to any charities at all. It thus seems like the morally best, least arbitrary way to allocate citizenship is to grant it to anyone in the pool of potential citizens who wants it.

While I argue that this should be our eventual goal, it is probably untenable at least in the short term. We must therefore keep birthright citizenship for now, on the grounds that getting rid of it would lead to morally worse outcomes.