Actually, this was incorporated into the User Agreement to allow PayPal the option of debiting a bank account WHEN legislation is passed [according to PayPal].
Because PayPal is neither a credit card processor nor a bank, it currently can not debit a personal bank account without account holder consent. Credit Card Processors and Banks however may. The legislation, pending passage, will expand coverage to non-bank and credit card processors, under certain circumstances.
The User Agreement IS misleading. As written, you WOULD presume legislation is in place and action can be taken now. It was PayPal's intent to incorporate this wordage in it's User Agreement so new accounts will not be caught unaware when it does happen.
One area where PayPal is heavy hit is credit card charge back fees - most of which can not be recouped without this legislation in place.