Can a former employee take IP they developed with me to a rival?

Generally, under Maltese employment and IP law, intellectual property created by an employee within the scope of their employment and duties typically belongs to the employer by default, rather than the individual employee, meaning the proprietary processes and documentation your former employee developed while working for you would generally remain your company's property, and your former employee would not have a legal right to take, use, or share this material with a new employer, regardless of their personal involvement in creating it. If your employment contract with this individual included confidentiality obligations, and ideally more specific IP assignment and post-termination restrictive covenant clauses, these would provide additional contractual grounds to act if you have genuine evidence they are using or disclosing your proprietary information, alongside your underlying IP ownership rights themselves. If you have concrete evidence, or a genuine, well-founded suspicion, that your former employee has taken or is using your proprietary materials at their new employer, this is a serious matter that could support both a claim against the former employee for breach of confidentiality or contractual obligations, and potentially action regarding misuse of your intellectual property, so it would be important to gather whatever evidence you have and consult a lawyer promptly to assess your strongest available legal options given the specific facts.