Davies Lavery has arranged for TT Club's case against the Home Office's fines for hauliers caught with illegal immigrants to be brought forward.
The Court of Appeal hearing, expected to last five to six days, started on Tuesday.
The case was originally due to be heard in March.
If Davies Lavery partner Kay Pysden wins the case, transport insurers may be able to claim back fines they have paid to the Home Office since April 2000.
The case involves a Turkish haulier, insured by transport mutual TT Club, which was fined £34,000 after one of its drivers was caught with 17 clandestine passengers in his vehicle.
