A court ruling won by the government warns climate change protesters that they could be jailed if they continue their campaign of blocking the M25.
Ministers hope the
High Court injunction can prevent further disruption around London.
Insulate Britain has blocked parts of the M25 five times in the last fortnight.
Transport Secretary Grant Shapps
tweeted that activists faced "possible imprisonment if they flout".
A large number of Insulate Britain campaigners have
been arrested at the protests, the first of which affected Essex, Hertfordshire and Kent on Monday, 13 September.
Protesters have also targeted other motorways, included the M11 near Stansted Airport in Essex and the M3 in Surrey.
The civil court action was taken by National Highways - the government body which runs motorways.