I am working in collaboration with another university where a collaborator was gathering data. He asked me to share my part, and I did as I assumed we were "collaborating". Now that he has all the database, he's no willing to share any of those data with anyone outside his university. I know that worst cases have happened to other researchers, so I am wondering, do we need to move from trusting in our fellow scientists towards legal protection? and how can I avoid this to happen again without losing trust in my colleagues?