How to know if a contract is enforceable or "void"?

Question

I read, for example, that specific cryptographic smart contracts are "not enforceable" in the legal context of them, and I understand that an agreement or a contract between parties that includes doing something illegal is void as well or "non-enforceable." If Peter signs a contract to give up his human rights, that contract would also be void, and probably the same for equality in many situations. But is there a general idea of how to know, or is it as simple as the idea of "non-disponible law" (not sure of the English word for it), which means some laws that hold no matter what the agreement has been made between two parties? In Sweden for example, the law of an individual, not representing an organization, who purchases something from a commercial company, cannot have rights that are less favorable than in the law of consumer (Kkl, konsumentköplagen), whereas between two commercial companies buying and selling something between them. Any agreement (within what is legal to do) will hold and enforceable according to "köplagen" (law of buying).

Answer 1

common-law

This is a broad question. You are basically asking for the content of several months of an introductory contracts course focused on the elements of contract formation and grounds for voidability. The best an answer can do at this point is to briefly list the factors that would have to be considered when trying to assess whether a contract exists, is enforceable, or is voidable. There are many other questions and answers on this site that get into the specifics of each of these.

1. Was the contract even formed?

   • was there an offer
   • was there acceptance
   • was there consideration
   • was there intention to create legal relations

2. Are there reasons why the contract would be void?

   • public policy grounds
   • a party lacked capacity
   • illegality
   • statutory overrides (like commercial codes or consumer protection acts)

3. Are there reasons why one party can void and rescind the contract or can ask the court for relief in the form of equitable rescission (the dividing line between these is debated and differs between jurisdiction)

   • mistake
   • fraud
   • duress
   • misrepresentation
   • others ...

I am almost certainly not covering all the possible ways that a contract might fail to exist or be void or voidable, and I don't intend to; this is meant only to give you a sense of the kinds of things that would go into the analysis. I have approached this through a common-law (and equity) lens as opposed to civil law, but even within the common-law world, there are differences between jurisdictions.

Answer 2

You know either by reading relevant information and hoping that you understand it correctly and that the person supplying the information understands it correctly, or by asking a lawyer.

Sorry, but that’s the answer. For a specific question, you can ask here.

There are also contracts that are “voidable”, that is the contract is enforceable until the second where one party decides to void it. For example contracts with minors quite often in many jurisdictions.