Let the employer file civil case then.

> Let the employer file civil case then

The IP theft is a private concern. The national security implications are public. What OP describes seems worth criminal investigation.

Is it?

I mean obviously if the said person did pilfer, or attempted to pilfer, it would be illegal.

But is there any law against interviewing for a job, while having a prior statement of intending to pilfer? Or in a more general sense, interviewing for a position while previously saying that they intend to breach the contract?

I'd imagine that there could only be ground for a lawsuit if 1) a contract has been signed, and 2) the stated activity has at least been attempted.