Please! Please stop insulting my brain!

For the second time this term, I caught students -what's the verb for plagiarism?

Including one who already did it before.

I can see that not everybody find the exercices the most exciting thing they ever had to do -fine- but a number of things are beyond me:

-considering it is perfectly acceptable (and even encouraged) to look up information from various sources and that refering to someone else's work is actually a good thing, why would one just copy whole paragraphs (WRONG), instead of integrating citations (GOOD)?

-hey, Google isn't exactly a well kept secret: any suspicious sentences can be looked up (and in this case, found) instantly. So, no, it does not take an elaborate device or advanced skill to catch you. Surprised?

-And this is especially true when the writer manages to leave over 20 spelling mistakes in three pages and then! magic! the writing style suddenly improves, finally there are no spelling mistakes, and finally, there is some content.

-When one can barely align two words correctly, one should really avoid using advanced jargon. I mean, come on.

I have to take drastic measures on this. What is not going to make my life easier is that this is in the course I am sharing with another prof whom I cannot expect to be tough on this.

I can already see them. Denying. Please, stop insulting my brain and treat people the way you want to be treated.

How do you deal with these things? What are the measures taken in your places for this kind of problems?