Do any companies use something more like a blackmailer's NDA, which works without a legal system?
I'm not sure exactly how it would work, and perhaps it wouldn't work in practice, but I imagine it might involve paying the (former) employee a certain sum every month for their continued cooperation, and the employer would reserve the right to unilaterally cancel the arrangement: it would be "discretionary" or whatever. So the employee has a motive to cooperate (unless they're terminally ill ...) but there's nothing to "enforce".
I'm not sure exactly how it would work, and perhaps it wouldn't work in practice, but I imagine it might involve paying the (former) employee a certain sum every month for their continued cooperation, and the employer would reserve the right to unilaterally cancel the arrangement: it would be "discretionary" or whatever. So the employee has a motive to cooperate (unless they're terminally ill ...) but there's nothing to "enforce".