Ok i got it - dunno why it works, but it is working for me, seems a little counterintuitive - i can only
guess it is skipping some error checking in another function:
you can cast this on a city with no essence - can't end the spell, but you can put a duration on it:
<Duration> 10</Duration> or however long you want it
 
<SpellDef InternalName="Governer's Orders 1">
     <DisplayName>Governer's Order 1</DisplayName>
     <Description>Governor target's a city to give 10% unrest </Description>
     <Image>S_Inspiration_Painting.png</Image>
     <IconFG>S_BlessCity_icon.png </IconFG>
     <IconBG>S_Inspiration_Icon_BG.png</IconBG>
     <IconColor>217,206225</IconColor>
     <AutoUnlock>1 </AutoUnlock>
     <CanStack>0</CanStack>
     <SpellBookSortCategory>City</SpellBookSortCategory>
     <SpellBookSortSubCategory>Other</SpellBookSortSubCategory>
     <SpellType>Strategic</SpellType>
     <SpellClass>ImpResourceBooster</SpellClass>
     <SpellSubClass>Other</SpellSubClass>
     <SpellTargetType>FriendlyCity</SpellTargetType>
     <GameModifier>   
               <ModType>Resource</ModType>
               <Attribute>Unrest</Attribute>
               <Value>-10</Value>
     </GameModifier>
     <HitSoundFX>Spell_BlessCity_01</HitSoundFX>
     <SpellCastEffectName>Brilliance</SpellCastEffectName>
     <SpellcastEffectScale>.2</SpellcastEffectScale>
      <SpellDefEffect>
           <EffectName>S_Inspiration_Particle</EffectName>
           <LocalPosition>0,0,0</LocalPosition>
           <EffectScale>.5 </EffectScale>
           <EffectDelay>.5 </EffectDelay>
           <SnapToTerrain>1</SnapToTerrain>
     </SpellDefEffect>
 </SpellDef>