Protesters targeting the M25 face being imprisoned for up to two years after a judge granted an injunction.
Transport Secretary Grant Shapps confirmed that National Highways had sought the legal ruling, which was granted last night.
Breach of the injunction can be punishable by up to two years in prison and an unlimited fine, according to the Department for Transport.
Campaign group Insulate Britain has caused chaos by disrupting traffic on the major motorway over the past week.
Surrey Police arrested 38 activists from the group, which targeted junctions 9 and 10 of Britain's busiest motorway at 7.57am on Tuesday.
Mr Shapps tweeted: "Invading a motorway is reckless & puts lives at risk.
"I asked National Highways to seek an injunction against M25 protestors which a judge granted last night.
"Effective later today, activists will face contempt of court with possible imprisonment if they flout."
Mr Shapps told MPs on the Transport Committee that he hopes the injunction will bring an end to the protests.
"Earlier in the process there was a somewhat different approach being taken," he said. "Yesterday the police were on the scene much more quickly. The injunction will greatly strengthen their hand."
He added: "We will review the powers because clearly it's unacceptable for people to be able to walk on to not just a major highway but a motorway, stop traffic, be released the next day and do the same thing again.
"An injunction may just be an interim way of doing that."
National Highways intend to return to court to extend the injunction and potentially seek additional powers of arrest, DfT said.
Home Secretary Priti Patel said the "important injunction" would mean "people can get moving again" on the M25.
"We will not tolerate lives being put at risk," she said. "Those who continue to do so risk imprisonment."
Insulate Britain, which is campaigning to improve home insulation, has been involved in demonstrations along the major motorway in Hertfordshire, Kent, Essex and Surrey over the past two weeks.
Tense scenes have shown protester walking out into moving rush hour traffic and causing havoc for motorists.
Insulate Britain confirmed it led the demonstration on Tuesday, saying recent rises in gas and electricity costs had "increased the urgency" for change.
Asked if the injunction would stop protests, Insulate Britain spokeswoman Zoe Cohen told the BBC: "The people taking part in these actions understand that the risks they are taking are because that we have tried everything else to make the Government protect us from the predicted impacts of climate chaos.
"That involves the loss of all that we cherish, our society, our way of life and law and order.
"We're calling for the installation and whole house retrofitting of social housing by 2025 and all homes by 2030, because this is the most effective way to reduce emissions, save lives from fuel poverty."
The High Court order, which officially came into force on Wednesday morning, prohibits anyone from "blocking, endangering, slowing down, preventing, or obstructing the free flow of traffic onto or along or off the M25 for the purposes of protesting".
It also forbids damage to the motorway surface, tunnelling nearby, erecting structures or obstructing the motorway on foot or in a car.
Mr Justice Lavender, who granted the injunction, said there will be a further hearing on October 5 at 10.30am.
