I suppose, depending on the lease, the landlord may be in the right legally. However the whole thing with the roommates sneaking into her room and searching it is way across the line, IMO.
I don't like to make gun and drug comparisons, but imagine if she decided to search the roommates' rooms and found heroin. I'm sure the roommates and all the people supporting what they did would be livid about the invasion of privacy.
I ccan't even get into the "guns will go off by themselves..."