Regulations to implement Congo’s new mining code have been signed into law with no changes, advisers to the prime minister told Reuters on Saturday, despite objections from mining firms that have been threatening legal action.

Prime Minister Bruno Tshibala signed the regulations into law overnight, his adviser Patrick Mutombo Buzangu told Reuters by telephone, but gave no further details.

The prime minister’s legal counsel Anita Lwambwa later confirmed that none of the changes being demanded by the mining industry had been made.

“The decree fully implements the mining code promulgated by the President of the Republic in March,” she said.

Mines Minister Martin Kabwelulu had told Reuters on Friday that no concessions would be made to the mining industry, which has demanded that key provisions be amended.

Congo is Africa’s top copper producer and the world’s leading miner of cobalt, an element which has seen a surge in demand to make batteries for electric cars.

Enacting the code is likely to trigger a legal battle between Congo and major mining companies, including Glencore and Randgold. The miners say the tax hikes and the removal of exemptions for pre-existing operations are a breach of their agreements with the government.

The new code, signed by President Joseph Kabila in March, axes 10-year protections for existing projects against changes to the fiscal regime, imposes a windfall profits tax and raises royalties.