BOGOTA – Colombia's constitutional court on Thursday ruled that local referendums that ban mining and oil extraction cannot halt energy projects, after a raft of votes spooked multinational companies.

A wave of environmentally focused anti-mining referendums over the past 18 months have worried investors, and forced some to alter investment plans, like AngloGold Ashanti which suspended a potential $2-billion project last year.

The ruling on the suit brought by Mansarovar Energy Colombia, a joint venture between India's ONGC-Videsh and China's Sinopec, was backed five to one by magistrates, the court said.

The Colombian Mining Association (ACM) said in a statement after the court decision it was now optimistic projects would get back on track.

"This decision not only gives life to several mining projects that would have been truncated by the (votes) but begins to give positive signals in terms of legal security," it said.

The previous government failed to legislate the issue, but President Ivan Duque, who took office two months ago, promised during his campaign to boost investment in the sector, which meant providing legal clarity to the mining sector.

The country's subsoil is national property and cannot be restricted by local authorities, the court ruling said.

The national government, however, cannot exercise sole control over extractive projects and Congress must pass regulations as soon as possible that allow communities to voice opposition to mining and oil projects, the court said.

There are 158 referendum initiatives in 135 municipalities nationwide, of which nine votes have been held, all against mining and oil exploitation, the ACM said.

Mansarovar brought the suit after residents of Cumaral municipality in central Meta province voted last year to ban oil exploration.

Mansarovar could not immediately be reached for comment.