As a rule it lacks civility (7,3)

I believe the answer is:

martial law

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'it lacks civility' is the definition.
The definition suggests a singular noun which matches the answer.

'as a rule' is the wordplay.
'as' becomes 'martial' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'a rule' becomes 'law' (law is a kind of rule).
'martial'+'law'='MARTIAL LAW'

Can you help me to learn more?

(Other definitions for martial law that I've seen before include "way to rule" , "Emergency powers" .)

I've seen this clue in The Globe and Mail.

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