Keith Bollinger’s paycheck as a factory manager had shriveled after the 2008 financial crisis, but then he got a chance to pull himself out of recession’s hole. A rival textile company offered him a better job — and a big raise.

When he said yes, it set off a three-year legal battle that concluded this past week but wiped out his savings along the way.

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“It’s not just that it allows employees to leave their company for another job,” said Mark A. Lemley, a professor at Stanford Law School. “It allows them to leave to start new companies.”