They are copyright protected.
If you buy them you can scan in and use by permission only
Most pro photograhers will allow personal copying for non commercial use.
You'll often find that those on the photographers' websites have the word 'PROOF' written right across them. They are not usually very high resolution either, so become quite blurred when enlarged.
It is fine to post a link to the website/photos, but it is an offence to 'take' the photos. Buying and distributing copies without the photographers permission is also a breach of Copyright.