Common interpretation maxims

 There are some common principles or presumptions as regards  legislation which are usually expressed in latin maxims which are resorted to in interpreting words in contexts in which they appear. They are explained below. 

1. The ejusdem generis principle : This principle shows that in a situation where there is a list of things which fall under an identical class,  followed by a general word, the scope of the general words is restricted to things belonging to the class to which all the specific or particular fall. You can consider this as a case of common noun and proper nouns..  let's say the law provides that biros,pencils and markers and all other writing aids should not be used. Such law covers other writing materials not listed here.

2.Expressio unis est exclusio atterius : the express mention of a thing is to the exclusion of others. This maxim of interpretation is of the provision that where the law explicitly mentions a thing or entity, such law is to the exclusion of others. Say the law states that no one should write with a 40 leaves exercise book, such would not extend to 50 leaves. 

3. Nositur a sociis : the idea of this maxim is that words should be interpreted in the context in which they appear. 

4. Lex non cogit impossiblia: the law does not compel the impossible. The law does not compel the doing of impossibilities.  The idea of this maxim is that the law cannot ask one perform any task which is humanly impossible because the law does not compel those under it to do what cannot be done.

5. Ut res magic valet quad paraet: that it may be effective, rather than be destroyed.  

  This applies where a legal provision is capable of two mutually exclusive interpretation one of which would make the provision valid and effective, and the other invalid, such provison must be interpreted in a way that it is valid.

References: 

Abiola sanni; Introduction to the Nigerian legal method.