Okay, legal eagles, have a little fun with this one.
The following situation actually happened in New Zealand:
A Christian youth group carried a barbecue on a youth group hike to the top of a mountain. There they had a cookout, had a nice time, presumably prayed and enjoyed the beauty of God's creation. When they came down, they were admonished by some sort of official in the Department of Conservation (i.e., a government agent) that they had been insensitive. The Maori regard the mountain as sacred, and cooking and eating food on the mountain is doing so "over an ancestor," which is offensive. (He added that it would have been different to carry food along and eat it for sustenance, a bit of animist cauistry that I'm sure will come in handy sometime.) The Christians apologized (which was foolish of them), and presumably they plan never to do such a thing again. The DOC says they are going to try to "build greater awareness" in the public of these taboos and that they "ask" climbers to "avoid standing" on the summit, because it's the most sacred part of the mountain.
Take this case; transport it to America. We'll imagine it's an Indian belief that the mountain is sacred. And just to make it really interesting, imagine that instead of staying in the realm of bullying bluff and bluster, where it is unclear what will happen if you blow them a raspberry and have another barbecue next weekend, the park commissioner and/or the relevant legislative body actually sets up regulations, with penalties, stating that no one is allowed to cook food on the top of the mountain or to stand in some marked-off area on the very summit of the mountain. Imagine that they do so expressly for the purpose of being sensitive to native "spiritual" sensibilities. (Of course, in the real world, they'd probably switch mid-stream, lie, and say that all this was needed to avoid forest fires and that standing on the marked-off part of the summit is too dangerous, but let's imagine for the sake of the thought experiment that they don't try that.)
By the logic of present American establishment jurisprudence, should such a regulation be regarded as an unconstitutional establishment of religion? Recall that Justice O'Connor's Lynch test, which some take to explicate and some take to replace the Lemon test, holds that an establishment of religion has taken place when a message of endorsement of a religion is sent telling "non-adherents that they are outsiders, not full members of the political community, and an accompanying message to adherents that they are insiders, favored members of the political community."