A contract can be declared unenforceable if a court is convinced that coercion was used to facilitate the signing. An example would be if blackmail was used as leverage to facilitate the contract. Courts can also declare a contract unenforceable when one of the parties to the contract has undue influence on the other.

What contracts are considered unenforceable?

A contract may be deemed unenforceable if one party obtains the other party's agreement by making false or misleading statements or omitting important information during discussions about entering into the agreement.

Under what circumstance the contract could become unenforceable?

To impugn a contract means attacking the integrity of the contract. A way it can be done is by deeming the contract unenforceable. A contract can be said unenforceable if it goes against the statutes of fraud or the Statement of Goods Act.