UPDATE 8:00 a.m. EST:
The British Parliament said it would introduce a bill to begin Brexit negotiations "within days" and will be as straightforward as possible.
David Davis, Parliament's Brexit secretary, said the ruling did not change the fact that Britain would leave the European Union.
Brexit has been put on hold -- for now.
The United Kingdom's Supreme Court ruled Tuesday that Parliament must approve before Prime Minister Theresa May can invoke Article 50, which will let Britain officially leave the European Union.
While Parliament is expected to ultimately approve of Brexit, this may allow members to soften Brexit's terms and hinder May's plan to begin Brexit negotiations by the end of March.
WATCH | Entrepreneur Gina Miller, the lead plaintiff in the lawsuit that led to the ruling, said she was "shocked" by the abuse she had taken for bringing the case to court.
To proceed otherwise would be a breach of settled constitutional principles stretching back many centuries.
May had said she would use the centuries-old political quirk of "royal prerogative" to invoke Article 50 without Parliament's approval. But the court ruled that the original Brexit referendum did not say what would happen as a result. To change the law to actually make the referendum effective, Parliament had to be involved.
The ramifications of the case were huge, as they would effectively determine whether the Prime Minister or Parliament actually holds power in the U.K.
However, Brexit is still likely to go through one way or another. It would be political suicide for a political party to renege on the referendum, which would likely be seen as a betrayal of the British people. But opponents of Brexit are likely to delay the legislation. Jeremy Corbyn, leader of the opposition Labour party, said his party would aim to keep the government accountable.
Unfortunately for businesses and other institutions, Brexit still means uncertainty.
Miller argued she did not intend to block Brexit, but to focus on the "dangerous precedent" of government overruling Parliament.
The new ruling also means that Scotland, Wales and Northern Ireland do not need to be consulted for Brexit legislation to pass. Scottish leader Nicola Sturgeon has warned the nation may try to leave the U.K. if it leaves the EU's "single market."
The Associated Press contributed to this report.