URI Class Security?

[eluser]web_wanderer[/eluser]
Greetings,

I was thinking of using the URI class and its segment_array() method to determine access privileges and filter data but am not sure how safe is that.

It'd basically go along the following lines:

Global constructor class gets the URI segments -> analyzes them -> assigns privilages -> filters data -> Loader loads the relevant page.

My question is - is it safe to filter data this way or can the URI be spoofed in some way so that it avoids the validation process altogether?