Possibly because "emergency legislation" is usually very poorly thought out, full of loopholes and badly applied? I mean it not like our government already has problems with legislation that ins't done in a hurry being badly thought out and having unforeseen consequences, or our politicians being so out of their depths they don't understand things like encryption can't be both secure and easy to bypass (or that the average person needs secure encryption, if just for banking).
A bit like the original version of the "materials likely to be useful for terrorism" that included things like tube maps, photos of locations, materials routinely used in university courses - under the definition of it old chemistry books and books aimed at kids from the 1900's could have been "materials likely to be useful for terrorism" as pretty much any chemistry book above a certain level will include information that can be used to create explosives (or sufficiently violent chemical reactions), whilst I remember having a book as a kid that told you how to make gunpowder (IIRC it was a kids activity book from the 50's or something).
Basically as applied initially if you looked wrong or came under suspicion for any reason anyone doing certain mainstream courses could have been found to be in possession of a myriad of "supporting evidence" - the old favourite "the anarchists cookbook" that some on here used to love talking about/trying to post links to would have done it.
