The government's Brexit bill will enable more British judges to depart from previous rulings of the EU's top court, Downing Street says.
The PM's spokesman said the Withdrawal Agreement Bill would expand this power to courts below the Supreme Court.
He added this would ensure judges at lower courts would not be "inadvertently" tied to the rulings "for years to come".
But others warned the move would cause legal uncertainty.
MPs are set for an initial vote on the withdrawal bill on Friday, after the Conservatives won an 80-seat majority at last week's general election.
Previous rulings of the European Court of Justice (ECJ) are set to be incorporated into the case law followed by British courts after Brexit.
The provision is contained in a separate EU withdrawal law passed in June last year under the premiership of Theresa May.
Previously, only the Supreme Court and the High Court of Justiciary in Scotland would be allowed to depart from these rulings.
Prime Minister Boris Johnson's spokesman said enabling lower courts to do the same was an "important change" to ensure they do not face a "legal bottleneck".
"We will take back control of our laws and disentangle ourselves from the EU's legal order just as was promised to the British people," he said.
There is no real detail in the government's pledge - but it marks a potentially really significant development.
It means that UK civil courts below the Supreme Court, for example the Court of Appeal, High Court, county courts, and tribunals such as the Employment Appeal Tribunal could depart from ECJ rulings in areas such as workers' rights.
Take for instance the right to paid holidays. The ECJ has interpreted this right more generously than the UK courts: for example, on the inclusion of overtime in holiday pay, and currently its interpretation binds the UK courts.
Following the 11 month transition period after Brexit, the way is open, for example, for an employer to take a case to one of the UK's lower civil courts and invite a judge to apply a more restrictive interpretation to the right to paid holidays.
This would create plenty of work for lawyers, but it opens a can of worms and could affect many workers.
The government's move was welcomed by former Tory leader Iain Duncan Smith, a leading figure in the pro-Brexit European Research Group.
"This is a critical pledge that puts sovereign rights back in the hands of the UK government and of course the British people," he said.
However, crossbench peer Lord Pannick QC, who acted for businesswoman Gina Millar in two cases against the government over its handling of Brexit, cautioned against the measure.
He told the Times, which first reported on the move, that allowing lower courts to depart from ECJ rulings would "cause very considerable legal uncertainty".
The government is hoping to get its Brexit deal through Parliament in the new year, enabling the UK to leave the EU by the end of January.
If passed, the UK would then follow EU rules during an 11-month transition period due to conclude at the end of December 2020.
MPs in the previous Parliament gave initial backing to the PM's Brexit bill but rejected his plan to fast-track the legislation through Parliament in three days in order to leave the EU by the then Brexit deadline of 31 October.
The government has already said the amended version of the withdrawal bill that will come back before MPs on Friday will include a new clause to rule out any extension to the transition period beyond the end of next year.