Foreign firms are mounting legal challenges over the Home Office's system for imposing fines on hauliers when migrants are caught hiding in vehicles.
Authorities can issue an on-the-spot penalty of up to £2,000 for every stowaway discovered.
The regime is set to come under scrutiny as two companies - one Romanian and one Dutch - take separate cases to the Court of Appeal.
Under the rules, road transport organisations and their drivers are required to secure vehicles coming into Britain to stop "clandestine entrants" using them to enter the country illegally.
The Romanian firm involved in one of the cases has paid out a total of more than £3,000 since the scheme began.
In 2013, three migrants jumped on to the roof of one of its trucks from a motorway bridge, cut through the tarpaulin cover and were found by British immigration officers during checks at Calais.
The company was fined £900 and the driver £600.
Marius Cuzmin, who manages the firm, told the BBC: "We are doing all we can, we're following all the guidelines ... we cannot do anything more than we are doing right now."
His solicitor Rupinder Matharu argued a "common-sense approach" was needed.
She said the system of penalties against hauliers, the code of practice and the underlying legislation are "ripe for review".
Ms Matharuis challenging the department on the grounds the firm followed guidelines on security, the driver checked the lorry three times before arriving in Calais and did not stop close to the port where many of the migrants gather.
The case is set to be heard by Lady Justice Gloster, Lady Justice King and Lord Justice Simon.
On Thursday, judges will hear another case in which a Dutch company is appealing against a fine of £7,200, according to the BBC.
Under the Immigration and Asylum Act 1999, those responsible for bringing "clandestine entrants" to the UK can be hit with civil penalties.
The Government's website says all road hauliers travelling to the UK must operate an "effective system" to secure vehicles.
The spotlight fell on the sanctions last summer as migrants made thousands of attempts to cross to Britain from Calais.
Figures showed the number of fines issued to hauliers more than tripled over three years, reaching more than 3,000 in 2014/15.
Last week, it was revealed ministers are considering extending the regime to rail operators.
The Home Office said it does not routinely comment on individual cases.
A spokesman said: "It is in all our interests to combat attempts to enter the UK illegally, which can damage the haulage industry financially and place the safety of drivers at risk.
"That is why we have invested tens of millions of pounds to reinforce security at our controls in northern France.
"The civil penalty regime is an important part of our wider response to tackle illegal immigration and exists to ensure that all drivers are taking reasonable measures to stop migrants from boarding their lorries.
"We are currently consulting on proposals to modernise the regime to reflect developments in both the technology available to hauliers and operators, and the tactics used by migrants."