It has been a grey area for most people for a long time ... the "Law" does state, and EU Law does state, you are permitted to make a "backup" of software you own.
HOWEVER, the EULA,
End User Licence Agreement, you enter into by reading the said EULA,
you do read them don't you? and you click the button agreeing to that said EULA will clearly state ... up yours jack, we do it our way, you lump it or leave it ... is one reason I NEVER AGREE TO THE EULA.
In fact, the license agreement for Microsoft
Office might leave you scratching your head ... It says
you can keep the original media after you install ... that’s your backup, pall.
The exception is if the disc is required to run the software. In that case, you can make one backup.
Please bear in mind, American Law don't stand for squidly here in the UK, so any "fair use" crap is out the window ... if in doubt READ THE BLOODY EULA. Or do as I do, never agree to one.