...We may make changes to the Terms from time to time, and if we do, we will notify you by revising the date at the top of the Terms and, in some cases, we may provide you with additional notice. Adobe will not make changes that have the effect of imposing additional fees or charges without providing additional notice. Any such changes will not apply to any dispute between you and Adobe arising prior to the date on which we posted the revised Terms incorporating such changes, or when the Terms otherwise become effective. You should look at the Terms regularly..."
"...Unless otherwise noted, the amended Terms will be effective immediately, and your continued use of our Services and Software confirm your acceptance of the changes. If you do not agree to the amended Terms, you must stop using our Services and Software and, if applicable, cancel your subscription..."
It doesn't have to be court-enforceable. It just has to be scary enough that the customer will self-enforce. Usually the worst thing that happens if you put something invalid in a contract is that it's as if you didn't write it. Which is fine because that's what you would have done anyway.
