In a blockchain like Steem, the contracts and therefore the law is codified in the version of the Steem software that witnesses run.

Community votes witnesses. Witnesses discuss possible changes to protocol and/or contract (like restriction on Steemit stake), devs code it, witnesses test it, witnesses deploy soft fork.

That's how a contract works in Steem.

So technically for Steemit Inc stake, the contract was in 22.1

If community does not agree, they change their witness votes. That's how it works.