What is the meaning of mens legislatoris?

Answer 1

Literally: «[the] mind of legislator», that is: his intent. Mens legislatoris is the ground upon which historical interpretation of Law is given. So, for those who support his interpretation of the Law on the will of the people who wrote the legal text, mens legislatoris is the main source of the meaning of an legislative act.

In the other hand, however, we have the ratio legis, or «[the] reason of the law». There's a logical meaning which flows from the Law itself, and that meaning comes from the literal words in it, from the context in which the law (or the section of the law) has been set in, and the status that the object of the Law had before the Law was given. All those factors («what the Law literally says», «where the Law has been located (among other Laws)», and «what has the Law came to change») made the ratio legis.

The fight of those two conceptions have been very hard in Continental Law. Common Law has historically free from that matter, but the increasing place the Law is taking in Common Law, is making take care about that point.