A weekly briefingfor Isabel.

In a 7-4 ruling handed down on 18 December, Spain's Constitutional Court held that a non-binding consultative vote on Catalan self-determination is not inherently unconstitutional, provided it is authorised by the Cortes Generales and does not purport to produce legal effect. The ruling stops well short of endorsing independence, and the minority opinion by four conservative justices argued forcefully that any such vote would undermine national sovereignty. President Salvador Illa of the Generalitat welcomed the decision as 'a door that has been opened', while Prime Minister Sánchez's spokesperson said the government would study it before commenting. The ruling places the political question firmly in the legislature for the first time since 2017.

The European Union's Carbon Border Adjustment Mechanism — the world's first carbon border tariff — moves from its transitional reporting phase to full financial effect on 1 January 2026. From that date, importers of steel, aluminium, cement, fertilisers, hydrogen and electricity must purchase CBAM certificates equivalent to the carbon price they would have paid under the EU Emissions Trading System had the goods been made inside the bloc. The current certificate price tracks ETS carbon at approximately €67 per tonne. The UK has announced a mirroring mechanism for 2027; the US has not.

Researchers at the Hospital de la Santa Creu i Sant Pau published Phase II trial results in The Lancet on 17 December showing that intrathecal injection of the antisense oligonucleotide jacifusen — targeting the C9orf72 repeat expansion that causes the most common familial form of ALS — halted disease progression for a median of 18.4 months across 64 participants. The control arm deteriorated at the expected rate of 1.3 points per month on the ALSFRS-R scale; treated patients showed a mean change of -0.07 points per month. Biogen, which licensed the compound from Ionis, announced an accelerated rolling submission to the EMA. A companion diagnostic for C9orf72 carrier status is required before treatment.

Paris-based Mistral AI released Mistral Large 3 on 19 December, a 72 billion parameter model it claims is the first frontier-class language model trained entirely on European infrastructure — specifically, a cluster of 4,096 H200 GPUs at Scaleway's Paris data centre. Benchmarks show performance on par with GPT-4o on standard tasks, with notably stronger performance on French, Spanish, Italian, German, Dutch and Polish. The model is available under a commercial licence that prohibits training derivative models above 70B parameters. Mistral also opened a 'sovereign deployment' programme through which EU public institutions can run the model on-premises.

A collaboration between CERN, ETH Zurich and the Max Planck Institute for Physics published a preprint on 16 December describing PhysicsLM-7B, a language model trained on 2.4TB of high-energy physics literature, LHC collision event records and detector simulation outputs. The model outperforms GPT-4o and Gemini 1.5 Pro on a new physics-specific benchmark by 34-41%, and — more significantly — can reason about detector artifacts in ways that general-purpose models cannot. The team said the model will be released to the physics community under an open-weights licence in January, with a companion tool for querying the CMS and ATLAS event databases.