You'll soon realize that law reading is not like any other type of reading you have ever done before. Just one of the ways that it is different is that it takes much, much longer to work your way through the material than you are used to -- especially at the beginning, when you don't know what is and is not important within the text. 10 minutes a page is about right, probably longer at first as you struggle to make sense of it all. Long story short: that 18-page assignment will take you roughly three hours to complete. Multiply that amount of time by your assignments for other classes and realize that your plan will have you spending an awful, awful lot of time in the library.
I think you answered your own question. You really shouldn't need permission to go to the library - if that's what you want to do, just go do it.