Jane Merrick is British political journalist and former political editor of the Independent on Sunday newspaper. The opinions expressed in this commentary are hers

(CNN) British Prime Minister Theresa May has always accepted that Brexit was going to be hard.

But now that the High Court in London has ruled against her and in favor of Parliament having a vote on how the UK leaves the European Union, she is finding that this will be a very hard Brexit indeed.

In his judgment, the Lord Chief Justice said that the "most fundamental rule of the UK constitution is that Parliament is sovereign and the Crown cannot overrule Parliament and can make and unmake any law it chooses."

The government had argued it did not need parliamentary approval to trigger Article 50, the mechanism for Britain to leave the EU, because the people had voted for this in the June 23 referendum. Why should MPs, it argued, delay or even stop Brexit if 52% of voters had already decided that Britain should leave?

Yet since the referendum, the Prime Minister and her team of Brexit ministers have not been clear about the exact terms of exiting the bloc.

May said she would trigger Article 50 by the end of March 2017, but there has been no concrete policy so far on whether Britain will continue to have access to the EU single market under a "soft Brexit" -- accepting the EU's rules on free movement of labour that such access requires -- or be out altogether, known as a "hard Brexit."

The referendum result -- in which 48% of people voted for no Brexit whatsoever -- did not make this clear, so it should not be for the government to decide on something so fundamental without parliamentary approval or scrutiny.

Last month MPs held debates on Brexit in the House of Commons, but as there was no binding vote afterward, the discussions were academic and toothless.

Too often, the House of Commons has been left powerless by government. The unwritten UK constitution rests on the separation of powers between the executive, legislature and judiciary branches. But in recent years there has been a creeping merger between executive and parliament.

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This High Court ruling will more clearly define the UK separation of powers, giving back more power to Parliament.

The government has said it will now appeal to the Supreme Court, which will rule on the case in early December. But it will be in the best interests of democracy if the Supreme Court upholds this judgment. The government should present its detailed case for Brexit to Parliament, and allow MPs to vote on what a UK outside of the EU will look like.

This does not have to expose Britain's detailed negotiating position with Brussels, but it should allow our democratically elected representatives to scrutinize the broad terms. It will also give the 48% who voted Remain -- 16 million people -- a voice that under the government's plans they are currently denied.

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Pro-Brexit MPs and campaigners are outraged by the High Court decision, claiming it is an attempt to subvert democracy. But there is no need for them to panic. This is not going to stop Brexit. The mood among MPs in Westminster, even those who have been leading the debate for the Remain side, is that Brexit will happen.

There are not many MPs who want to overturn the referendum result. If that were to happen, there would likely be a public revolt.

Ultimately, MPs will vote to give Article 50 the go-ahead, but only after the terms of Brexit have been debated and scrutinized. Anyone who passionately believes in democracy should be happy with that.