What legal principals limit the ability to change terms of contract?

Answer 1

The legal term for changing the terms of a contract is "stipulation". This means both parties must agree on the change.

Answer 2

I only know SA law, which is based on Roman law. But the basic principle is 'caveat subscriptor': 'let him who signs beware'. This means that if you sign something, you will have to go through with it.

A non-alteration clause is standard for preventing changes that aren't in writing (it says something along the lines of 'no changes to this contract will be valid unless they are in writing and signed by both parties').

Even with this clause, sometimes people get out of the contract by cancelling it verbally (the clause only mentions CHANGES, not TERMINATION). So sometimes people add in a non-cancellation clause ('this contract may only be cancelled in writing').

A good lawyer can get around both of these by claiming that the one party waived their rights in terms of the contract (ie temporarily gave up their rights). So really strict contracts add in a non-waiver clause ('no waiver of any terms of this contract will be valid').

With all these clauses in, you have all your bases covered - and a contract which hugely privileges the person who draws it up. If you come across a contract with all these terms included, you may have no choice but to sign it (eg buying a plane ticket), but be aware that it puts you at a big disadvantage.

ps: as a law student, I'd better put a disclaimer on all of this in case it's wrong. I have a friend who even puts disclaimers on her restaurant recommendations!

Answer 3

All parties that are involved in the contract must agree to and sign any changes.