Civil Code § 3422

Except where otherwise provided by this Title, a final injunction may be granted to prevent the breach of an obligation existing in favor of the applicant:

1. Where pecuniary compensation would not afford adequate relief;

2. Where it would be extremely difficult to ascertain the amount of compensation which would afford adequate relief;

3. Where the restraint is necessary to prevent a multiplicity of judicial proceedings; or,

4. Where the obligation arises from a trust.