A group of British airports and airlines have taken the UK government to court, demanding it disclose the evidence behind its coronavirus travel restrictions that they say is ruining their business. Manchester Airports Group says the government’s “traffic light” system of classing countries as low, medium, or high risk, is not transparent.

“We are told it is a risk-based approach, so what we say is that the criteria and the reasons must be sufficiently accessible,” stated a lawyer for the Group, owners of Manchester, Stansted and East Midlands airports, which brought the case along with airlines Ryanair, Virgin Atlantic and easyJet, travel operator TUI and British Airways’ parent company, IAG.

Tom Hickman said at a High Court hearing in London on Friday that there was a “fundamental lack of transparency” and the categorizations appeared arbitrary.

Only 27 countries and territories are on the “green list,” which allows British residents to travel there without having to quarantine on return. Arrivals from dozens of “amber list” countries have to self-isolate at home for 10 days, while people arriving from “red list” countries including India and Brazil must quarantine in a government-approved hotel.

The government says it will lift the self-isolation requirement for fully vaccinated Britons returning from amber list countries on July 19.

The government’s lawyer, David Blundell said that “decisions need to be made urgently, in response to emerging data” and forcing disclosure of all the evidence “would lead to a serious risk of delay in a decision-making process.”

The two judges hearing the case plan to give their ruling at a later date.