In my opinion, restricting study materials is counterproductive (particularly if no computer-searchable version of the course textbooks exist.) I realize that blindly copying answers is bad, but cheating on coursework has always been a problem and it is an issue that is independent of the Internet.
One common complaint is that students will learn less by Googling than they will by reading the textbook. This may or may not be true, but being able to search gives the learner access to much more targeted information. The difference between needing to skim through fifty pages you already understand in hopes of finding a paragraph you didn't, and being able to immediately enrich yourself on the topic desired, is phenomenal.
The thing is, the anti-Google teachers are right about one thing - you aren't going to remember how to use it practically if you don't actually use it. One answer here said that the degree of the problem became apparent when an in-class test revealed that the students, who up until then had been passing relentlessly difficult questions with ease, knew next to nothing.
This is actually a really useful thing to know, because armed with that knowledge the real problem becomes apparent - the students aren't using their research, which is why it isn't 'sticking.' A great option would be to hold a brief, three- or five-question test before each class - placing numerous, smaller checkpoints along the way will teach the students how to learn the material and retain it for use far better than either cramming or Googling together a paper.
I'm going to go one step further, though, and say that this also illustrates a deeper need for education to evolve. We don't live in the dark anymore - we live in an age of effulgence, where learning of any sort is a phrase away. To educate successfully, it will become necessary to embrace this by teaching more applied mathematics and asking more questions. To wit, if the course itself demands knowledge, the students will learn.
That said, I do not at all approve of students asking for (or receiving) verbatim solutions, either online or from classmates. This is cheating no matter where it takes place.