Magical Light on Asteroid Cities

I need a reason for why PRIVATE, i.e. not government-approved magical 
light sources might be forbidden on an asteroid city(1). I found it in 
thatotherguys dragon rock writeup:

"The final category of laws are the civil laws.  These laws are ones 
against littering, digging more than two levels deep into Dragon Rock, 
placing continual ligth spells or luminescent substances on your of, and 
similar acts that regulate common order but have little to do with actual 
crime (though it is, of course, a crime to violate these laws). "

I'm not a native english speaker, so I have no idea what "on your of" 
means. Please enlighten me!

Anyway, I like the regulation of banning some "private" light sources. It 
gives the city a unique flair. But I need a reason for the ban, however 
flimsy it might be. 

I think even the existence of a "Lantern Guild" might be enough reason: it 
has a quasi-monopoly on artificial light sources that are not fire-based.
Torches and other fire-based light sources are not banned, but are heavily 
taxed based on a government-approved list. The amount of tax is linked to 
the amount of air they consume. Every business selling non-firebased light 
sources has to acquire a government licence, which is - due to the 
successful lobbying of the guild - quite hard for non-guildmembers.

...other ideas?

(1) I'm trying to re-create Dragon Rock (losely based on thatotherguy's 
superb writeup), that's why I'm asking asteroid-city- related questions 
now and then.