Disable the submission of a form I need to make a form read-only under certains conditions : what I did is to not add the $form['submit'] button.

This way I can't submit the form. But I wonder if it is enough ... 

Do you know if I ca be 100% sure that nobody could find a way to submit the form ?

Thanks !
To make sure nobody submit the form create a custom validate function that always set error on form ,(using form_set_error).

In that validate function you have to check for the circunstnaces that makes the form available to submission or not.