To my knowledge there are 2 ways to get this. One is from an event, considered a 'Crisis' that comes from your choices. The other is an influence effect. Check the diplomacy screen and look to see if you are being pushed by other empires into the red. Odds are you were pushed into sanction territory and had someone slap you with a diplomatic demand with the consequences for refusing being a 50% law upkeep for X number of turns.

how do you see turns remaining on the crisis?

The number of turns will depend on the game speed and will either be listed in the government panel (do forgive as I forget where off the top of my head) or in the diplomacy panel when you select the empire that is imposing the penalty. (this should appear in the top right when you open the folding menu)

If you are running on Fast or Normal this effect should only last 5-10 turns. On Endless you are looking at a 20 turn long debuff so it heavily pays to keep tabs on the popups you get as well as diplomatic power against you.

cheers ty