The Government is set to find out the result of an appeal court battle to prevent thousands of individuals who had jobseeker payments stopped from clawing back millions of pounds in lost benefits.
It is fighting to block an estimated £130 million which could be repaid in the wake of a Supreme Court ruling in October 2013.
Five justices at the highest court in the land ruled, in what became known as the Poundland case, that the Government's flagship back-to-work schemes were flawed because sufficient information had not been given to claimants to enable them to make representations before benefits were stopped.
The Government brought in emergency retrospective legislation, the Jobseekers (Back to Work Schemes) Act 2013, to "protect the public purse" and stop the payouts.
It was argued the sanctions had been justified and the claimants would be receiving "undeserved windfall payments".
But a High Court judge, Mrs Justice Lang, declared the 2013 Act "incompatible" with Article 6 of the European Convention on Human Rights, which protects the right to fair hearings.
The Department for Work and Pensions (DWP) decided not to make any payouts pending the Court of Appeal bid to overturn Mrs Justice Lang's decision.
At a hearing in November, James Eadie QC, for the Work and Pensions Secretary, told three judges in London that the 2013 Act was necessary to prevent payments being made to individuals who had refused "without good reason" to take part in back-to-work schemes and accordingly been sanctioned.
The QC said, if the appeal failed, "up to £130 million might need to be found from the welfare budget at a time of austerity".
Mr Eadie said the High Court decision was "wrong in law" and Mrs Justice Lang had "failed to afford the necessary constitutional respect to Parliament and the parliamentary process".
The 2013 Act was primary legislation dealing with social security policy debated and passed in Parliament and accordingly entitled to constitutional respect.
The original Supreme Court ruling was won by university graduate Cait Reilly, from Birmingham, who challenged having to work for free at a local Poundland discount store.
Ms Reilly and unemployed HGV driver Jamieson Wilson, from Nottingham, won the original ruling that regulations governing the back-to-work schemes were flawed.
Mr Wilson objected to doing unpaid work cleaning furniture, and as a result was stripped of his jobseeker's allowance for six months.
Ms Reilly was joined in the battle against the subsequent emergency legislation by another jobseeker, Daniel Hewstone, who has received jobseeker's benefits since 2008.
The court was told Mr Hewstone stopped attending the DWP's Work Programme because he could not afford to wait for his travel expenses to be reimbursed and felt that the menial work offered did not enhance his skills or improve his prospect of finding long-term work.
Lord Justice Underhill, Lord Justice Burnett and Dame Janet Smith will announce their decision in the appeal on Friday.