Govia Thameslink has secured an injuction against rail union Aslef over its members' refusal to drive new, longer trains on the Gatwick Express, the company said.
The company took its case to the High Court in London after accusing Aslef members of refusing to drive the first services that were due to operate in 12-car formation in recent days.
The union is planning to ballot its members for industrial action over the dispute, saying it has never reached an agreement for the new trains on the Gatwick Airport to London Victoria service.
A spokesman for GTR said: "We are pleased that the court has granted us an injunction that Aslef must not induce our drivers to refuse to operate the new 12 car trains. Gatwick Express services have operated without conductors operating the doors for 17 years, so we were never able to understand why the Aslef union objected to the operation of these new trains in the same way.
"The new trains will offer significant benefits to passengers including a much better travelling environment. We plan that by June 50% of weekday services will operate with 12 cars and we will now commence their introduction into service.
"We took this action with great reluctance but were left with no alternative by the approach of the Aslef union. In respect of the other disputes presently ongoing, we hope this ruling today will influence the trade unions to come back to the negotiating table and avoid going ahead with any unnecessary and damaging strike action on this or any other issue."