Re: [platypii] State Park Legality
To my knowledge, National Forests are viewed the same as BLM land. That said, not all National Forest rangers are aware of this, so watch your back.
With regard to your second question, if you exit outside a National Park and land inside, courts have interpreted that to be a breach of the aerial delivery statute (see: U.S. v. Albers et al. 9th Circuit, 2000. At section three). We actually have a case involving this issue going on right now (on which I can't comment further at this time).
However, if you were to exit
inside a National Park and deploy your canopy
outside said National Park, that would likely be another issue (although the NPS may not see it that way if you got caught).
Finally, there's also the issue of jumping national monuments, which I believe to be a no-no. I haven't dealt with this directly; somebody who has more knowledge on the subject can chime in.