It’s a constitutional decision because we ar are not ruled by a tyrannical dictatorship
A lot of government policy is set via contracts. Minimum wages, diversity, etc.
This drops a nice little bomb into it. Previously, it was held that a contract can be anything, so the courts where very hesitant to interfere. Heck, there are NDA’s that explicitly limit you from reporting criminal offenses. When Snowden’s claims first came out, I did not hear anyone at alphabet soup saying he was wrong, but a lot of people saying he violated his contract.
I will defer to lawyers here, but this is an interesting precedent. And in my opinion a good one.