I'm British—so why can't I vote in the most important British election in years?

I’m a 43-year-old British citizen. I was born and raised in Britain, and I carry a British passport whenever I travel. Britain’s status in the international community is extremely important to me. And yet, like millions of other British nationals, I’m not allowed to vote on the most important issue in recent British history.

On Thursday June 23, the United Kingdom will hold a crucially important national referendum. The question: “Should the United Kingdom remain a member of the European Union, or leave the European Union?”

No one knows how the British electorate is going to end up voting; right now the polling consensus is that it’s very close to a 50-50 nailbiter. If Britain does leave the EU, however, the consequences, both for the UK and for Europe, would be horrible.

All Europeans, then, are deeply invested in the outcome of this vote. Certainly all British citizens are. But Britons in Europe—those living in Ireland, say, or Spain, or any of the other EU countries—will be the most directly affected, getting the worst of both worlds. If Britain does vote to leave the EU, they could end up losing all their rights to live, work, and get healthcare in the country that they might have called home for decades.

And here’s the scandal: according to the rules of the referendum, only British citizens living in the UK will be allowed to vote. The most committed British Europeans—the ones who have made their home elsewhere in the EU for more than 15 years—will have no say in the referendum whatsoever.

The problem lies in Britain’s ancient parliamentary democracy. The country’s national elections take place in 650 different local constituencies: all of the 650 members of parliament, or MPs, represent one small area each. (Prime minister David Cameron, for instance, represents Witney, a town just west of Oxford.)

Britain’s parliamentary system causes a problem for people who have not lived in the country for many years. Wherever they might have happened to live decades ago, they don’t live there any more, and so it makes a certain amount of sense that they shouldn’t elect a representative from that particular area. Under UK law, after 15 years you’re deemed to have left the country for so long that you really have no business voting.

That might be defensible when people are just voting to elect their local MP. Referendums, however, are very different. In a referendum, it makes no difference what constituency you’re in, and as a result the place where you live (or don’t live) should be irrelevant.

This referendum is the most significant vote of my lifetime, and I very much want to vote for Britain to stay part of the European Union. And there are millions of others like me: some 5 million, altogether, of which about 1 million are in the EU.

If Britain is serious about being a democracy, it should give every adult with a British passport the opportunity to vote in this election. The only reason not to is sheer laziness: the electoral system is set up for constituency-level voting, and it would involve a certain amount of work to give the vote to ex-pats as well.

But that’s work well worth doing. It’s long past time for Britain, the world’s oldest democracy, to enfranchise its British diaspora, if only for referendums. After all, this election result needs all the legitimacy it can get. Leaving Britain’s ex-pats out in the cold is not going to do that.