The Withdrawal Agreement Act removes the last U.K. obstacle to the country leaving the European Union (EU) in just over a week.
Speaking in the House of Commons on Thursday, Deputy Speaker Nigel Evans’ announcement that the queen had signed off on the law drew cheers of "Hear! Hear!" from some Conservative lawmakers.
"At times, it felt like we would never cross the Brexit finish line, but we've done it," Prime Minister Boris Johnson said.
The EU Parliament must ratify the Brexit divorce deal before Jan. 31, Britain's scheduled departure date. The EU Parliament's constitutional affairs committee voted by a large margin Thursday to approve the Brexit withdrawal deal, preparing the way for a vote of all European lawmakers in Brussels on Wednesday.
"It's a historical moment, albeit a somber moment, for us. We deeply regret this outcome," committee chair Antonio Tajani said after the 23-3 vote.
After years of negotiations between the British government and the EU, U.K. lawmakers repeatedly defeated attempts by both Johnson and his predecessor Theresa May to finalize Britain's departure terms.
But that changed when Johnson's Conservatives won Britain's Dec. 12 election, giving his 80-strong majority in the Commons the ability to overrule the objections of opposition parties.
Despite Johnson's repeated promise to "get Brexit done" on Jan. 31, the day of departure only marks the start of the country's exit from the EU.
Guy Verhofstadt, the leading EU lawmaker on Brexit, said the bloc's parliament would continue to scrutinize the way Britain implemented the divorce agreement.
Britain and the EU will begin negotiations next month on their future ties, racing to strike new relationships for trade, security and other areas by the end of 2020. Johnson insists he won't agree to any delays in those talks beyond the end of the year.
The Associated Press contributed to this report.