This question deals with PhD programs which guarantee their students funding via teaching assistantships in the US.
In order to have more time for themselves (e.g., for PhD research, or for working a higher-paying part-time job), are PhD students normally allowed to decline teaching assistantships, as long as they're willing to forgo the department's stipend?
In addition to losing the stipend, are there other disadvantages to declining a TA position? (E.g., would tuition no longer be free?, could the department be frustrated?, etc.)