In The Merchant of Venice, a malicious contract (demanding the famous pound of flesh) is itself viewed as a criminal act worthy of punishment. If this is the kind of language vendors are sneaking into contracts, that would be a fitting solution to the problem.
Note that it's not the contractualism, but the fact that Shylock is Jewish:
Tarry, Jew:
The law hath yet another hold on you.
It is enacted in the laws of Venice,
If it be proved against an alien
That by direct or indirect attempts
He seek the life of any citizen,
The party 'gainst the which he doth contrive
Shall seize one half his goods; the other half
Comes to the privy coffer of the state;
And the offender's life lies in the mercy
Of the duke only, 'gainst all other voice.
("Alien" means any non-citizen, but it's clear that it's specifically because Shylock is Jewish.)
Because it was done in a contract, it counts as an "indirect attempt", but it's the same law as if it were a physical assault.
(Also note: nobody else in the room seems to have ever heard of this law, and nobody brought it up. Portia is not, in fact, a lawyer. Nobody bothers to check the texts. Antonio's life is already safe; there is no need to heap additional punishment on Shylock. I believe that Portia is just making it up, and everybody goes with it.)
