Spoken promises of job security can even supersede a written "at-will" statement, which says employees can be terminated at any time for any legal reason.
Case in point: A California company recruited a New Jersey man for a multiyear project. When the man said he'd move his family to California only for a permanent position, the hiring manager agreed orally that the position would be permanent. Two years later, the project ended, and the company fired the man.
He sued for negligent misrepresentation and won. The court said the oral promise was enough.
The lesson: You should always avoid making, or even hinting at, guarantees about long-term job commitments. Avoid statements such as "You'll be with us as long as you can do your job well," or "You'll have lots of job security here."
By talking up job permanence or making other lofty promises, you could crush the organization's ability to fire people or lay them off if needed.
Beware that courts will be even stricter in enforcing such implied contracts when, as this case shows, applicants make special sacrifices to take the job.