An object or agreement is considered illegal if: 1) It is forbidden by law or would defeat the provisions of any law. 2) It is fraudulent or involves injury to another's person or property. 3) A court regards it as immoral or opposed to public policy.

1. Legality of Object

2. Object is unlawful
 If it is forbidden by law.
 If it is such a nature that, if permitted, it would
defeat the provisions of any law.
 If it is fraudulent.
 If it involves or implies injury to the person or
property of another.
 If the court regards it as immoral.
 Where the court regards it as opposed to public
policy.

3. Every illegal agreement is unlawful, but
every unlawful agreement is not
necessarily illegal.

4. Effects of illegality
 Ex turpi causa non roritur actio.
 In pari delicto, potior est conditio defendentis.
 Whether illegality is severable.
 Reciprocal promises.
 Alternative promise, one branch being
illegal.
 Agreements void, if consideration and
objects unlawful in part.

5. Agreements opposed to public policy
 Agreements of trading with enemy.
 Agreements to commit suicide.
 Agreements which interfere with
administration of justice.
 Agreements in restraint of legal proceedings.
 Trafficking in public offices and titles.
 Agreements tending to create interest opposed
to duty.

6. Agreements opposed to public policy
 Agreements in restraint of parental rights.
 Agreements restricting personal liberty.
 Agreements in restraint of marriage.
 Marriage brokerage or brocage agreements.
 Agreements interfering with marital duties.
 Agreements to defraud creditors or revenue
authorities.
 Agreements in restraint of trade.

7. Trade combinations

8. Service contracts