That's true of many illegal things. Trespassing is illegal, but people still put locks, gates, fences, etc on their property because people will still trespass if they want to. The purpose of the law is to dissuade people from doing it because there are consequences for that action.
If you're talking about trade secrets, I believe if there is evidence in the product/products that a former employees company is releasing that seems to be operating or working in a similar product they could gather publicly available evidence, hire a PI, and ultimately attempt to subpoena additional information if there is sufficient evidence that the employee is actually sharing trade secrets from a previous company.
If you're talking about trade secrets, I believe if there is evidence in the product/products that a former employees company is releasing that seems to be operating or working in a similar product they could gather publicly available evidence, hire a PI, and ultimately attempt to subpoena additional information if there is sufficient evidence that the employee is actually sharing trade secrets from a previous company.