When it comes to using slide-outs in Rest Areas, there is no "of course you can" or "of course you can't".
This I-30 Rest Area just west of Malvern, Arkansas is an example where good judgment must prevail.
I used my slide out less than a foot (out of 3 feet) to avoid blocking the sidewalk.
At full 3 foot slide-out deployment, it's likely to piss off somebody walking down the sidewalk at 2 a.m. when you have blocked the sidewalk.
If you have slide-outs on the other side, they would obstruct traffic in the acceleration lane to merge back on to the interstate highway.
I find this to be a somewhat dangerous rest area for camping and avoid it if I don't need the rest.