Let's turn the sentence around first, to see it in the standard format of a conditional sentence.
If they are kept out of sight it may be possible to limit the harm caused to society by the operation of illegal drug markets.
Now, what does a type 1 conditional look like?
It has a possibly true condition followed by a statement of consequence, typically in the future.
The topic sentence looks to me like a normal type 1 conditional.
If they are kept out of sight - a possibly true condition.
... it may be possible to limit ... - a statement of future consequence.
The fact that the future consequence is expressed as a possibility rather than a certainty doesn't change the fact that this is a first conditional statement.