Software code copied by ex-employee — is this trade secret or copyright violation?

Both are available and you should run them in parallel. Copyright: software code is a copyrighted work under Federal Law 38 of 2021; substantial similarity (including comments + variable names) is strong evidence. Trade secret: if the code embodied confidential algorithms or proprietary architecture, Federal Law 36 of 2021 (Trade Secrets) gives separate damages including injunctive relief. Preserve evidence forensically — git history, access logs, his employee NDA and IP-assignment clauses. Both claims at the Federal Court; ex-parte injunction is available to preserve evidence at the new employer.