Would someone mind explaining to me a piece of Religious terminology? Thank you. (Warning -Hamlet spoilers and mentions of suicide)

I'm studying Hamlet for my Literature coursework, and there is a word that I'm not completely sure of the definition for. The word is 'canon'.

The quote is: 'Or that the Everlasting had not fixed His canon ‘gainst self-slaughter’.

The quote basically means that Hamlet would like to commit suicide but won't because he believes that God thinks it's wrong.

I think canon means something like 'law' but I'm not quite sure. I'd like to analyse it as part of my coursework though so if someone would mind helping me that would be great :D