ACS:Law and its one solicitor, Andrew Crossley, sent thousands of letters threatening recipients with court action if they did not pay out.
Now a judge has ruled that the company may be responsible for wasted costs in the case and ordered a full hearing.
Mr Crossley's lawyers declined to comment.
The proceedings represent something of a role reversal. Originally the Patents County Court had been asked to hear the cases brought by Mr Crossley's firm.
After those collapsed, it was decided that he might be liable for costs.
Those could run into thousands of pounds, although that money is likely to be covered by solicitors' insurance.Lawyer's letters
ACS:Law had originally teamed-up with a company called MediaCAT, which purported to represent copyright owners, such as film and music producers.
Together they sent letters to around 10,000 people in the UK, alleging that the IP addresses of their computers had been linked to illegal file sharing.
Individuals were given the option of paying £500 or facing court action.
Many of those contacted said they had never engaged in such activity and accused ACS:Law of carrying out a speculative "fishing" exercise.
Mr Crossley eventually brought 26 cases to court, but soon after hearings began he tried to have them dismissed, claiming he had been attacked and received death threats.
Judge Colin Birss QC refused to allow proceedings to stop and accused Mr Crossley of trying to "to avoid judicial scrutiny".
Soon after, both ACS:Law and MediaCAT were wound-up.Profit share
It emerged in court that the two companies had agreed on a profit-sharing model, with ACS:Law receiving 65% of any money recovered.
In his most recent ruling, Mr Birss said that arrangement had "brought the legal profession into disrepute".
He also branded the now-defunct firm "amateurish and slipshod".
The court's decision to press ahead with a hearing on wasted costs was welcomed by lawyers representing those people who received ACS:Law letters.
Michael Forrester, from Ralli Solicitors, said his firm was also planning to pursue claims for harassment against Mr Crossley and urged anyone who was affected to join the action.
"It can be incredibly upsetting for people to receive these letters and they may well have a claim in harassment, so I am urging them to come forward."
Mr Crossley's application for permission to appeal was refused. He is also being investigated by the Solicitors Regulation Authority.
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