> How will this be enforced?

Probably through penalties listed in the contract, or simply suing for breach of contract.

While many US states allow at-will agreements that allow either party to depart at any time for any reason without penalty, as far as I know, you're not required to be employed at-will if both parties agree to the terms of the contract.

While it's a somewhat special case, I know the US federal government often employs people with though-shalt-not-break-without-penalty contracts. Examples are military service, and many of the higher-education loan-forgiveness programmes.

The two year commitment is based on a verbal agreement between you and the employer if you are invited to interview. We just want someone that will stay with us for a good length of time.

Yes, this is a real job post.