Snapshot: In March 2025, seven farmers from the Tambo River Valley, located in the Arequipa region of southwestern Peru, filed a legal protection action (acción de amparo) before the First Constitutional Court of Lima against Southern Peru Copper Corporation (Group Mexico), the owner of the Tía María copper project, as well as several governmental authorities involved with its authorisation process. The claimants allege the Environmental Impact Assessment (EIA) expired in 2019 and the project should not be authorised. The case is ongoing.

The Tía María project of Southern Peru Copper Corporation consists of the Tía María and La Tapada copper deposits and is located in the Tambo River Valley in the Islay province of Arequipa, Peru. It has faced sustained opposition from the local farming communities since 2009, when the project’s Environmental Impact Assessment (EIA) was first submitted.

In September 2009, local communities organised a popular consultation on the project, in which 97% voted against it. Since then, the opposition has continued, marked by protests and strikes, as well as deaths, arrests, and judicial proceedings against leaders and protestors.

Opposition to the project stems, among other reasons, from concerns about its potential effects on local water sources and agriculture, the main livelihood of local communities.

The first EIA was declared inadmissible in 2011 due to numerous technical deficiencies. However, in November 2013, the company submitted a new EIA which was approved in August 2014. The approval led to a renewed wave of protests and repression in 2015, and the project did not advance due to the unrest.

In July 2019 the government granted the construction licence to the company to start the works. However, following further unrest, the Mining Council (an administrative tribunal) suspended the licence in August 2019, with the government and the company agreeing that the project would only move forward when the social conditions improved.

In 2024, the company announced it was seeking to move the project forward and start the development works, stating that conditions had improved. The announcementtriggered renewed protests.

On 21 March 2025, seven farmers from the valley, five men and two women, including leaders of local organisations opposing the project, acting as representatives of the local communities and supported by organisations such as FEDEPAZ, Red Muqui, and CooperAcción, filed a legal protection action (acción de amparo) before the First Constitutional Court of Lima. The action was brought against the company, the Ministry of Energy and Mines, the Body of Environmental Evaluation (OEFA) and the Sustainable Investments National Certification Service (SENACE).

The claimants argue that the EIA expired in 2019 and that the project poses important environmental and social risks, including impacts on the right to a clean, healthy and sustainable environment. They also content that the project does not have the consent of local communities. They request that the court declares the EIA expired and ordersthe company not to continue seeking authorisation for the project.

On 1 July 2025, the court admitted the lawsuit and set a virtual hearing for 2 October 2025. However, the hearing was later rescheduled for January 2026 and subsequentlysuspended again without a new date being set. The case remains ongoing.

Meanwhile, on 13 October 2025, the Ministry of Energy and Mines authorised the company to start the exploitation works, prompting local communities to announce renewed opposition. On 28 October 2025, the claimants asked the First Constitutional Court to suspend the authorisation as a precautionary measure and, on 3 November 2025, the provincial government of Islay filed an administrative appeal against the authorisation before the Mining Council.

On 19 March 2026, in response to the this appeal, the Mining Council annulled the authorisation because it considered it missed the assessment of some legal requirements. Nevertheless, on 17 April 2026, the Ministry issued a new authorisation of the start of the exploitation works. Due to the possible resumption of the project, residents of the Tambo Valley have announced the launch of various nationwide protests. The works on the project are advancing, and the company intends to start operations in 2027.