This is definitely a workaround, but I think you could meet the letter of the law by accessing the Exchange server through a web browser that's configured to never cache anything.
Assuming Web Services are enabled, naturally.
The problem is that in the course of my field work I quite often find myself in places where I can't find Ethernet or open Wi-Fi, thus making me reliant on my phone. I'd prefer not to tether (easy on a rooted Droid with a grandfathered unlimited VZW data plan) as it's hard on the phone (you should see the temperature spike as data rates increase) and it adds to the space I need to occupy in places where my space allowance is often a chair and a 3'x3' table, although doing so would meet the letter of the standard. I'd much rather leave e-mail to the phone and put the laptop back in the bag so I have more space to get my work done, thus leaving me with the requirement to meet a standard that my centralized IT boffins cribbed from some "best practices" document without doing the slightest bit of research into whether or not the standard is achievable at not-ridiculous costs.
We've asked Central IT to give us a list of phones that meet their standards. They refused, saying that the analysis of compliance and the required personal signature on the policy stating that our phones comply with their policy is our problem.
I so adore check-box engineering.
If the Earth were flat, cats would have pushed everything off of it by now.