From the Shenandoah NP website, you have three hoops to jump through -- federal, state and local:

Firearms in National Parks

The law governing possession of firearms inside a national park changed on February 22, 2010.

Visitors may possess firearms within a national park unit provided they comply with federal, state, and local laws.

The role of the responsible gun owner is to know and obey the federal, state, and local laws appropriate to the park they are visiting.

Please remember that federal law prohibits firearms in certain park facilities and buildings. These places are marked with signs at public entrances.

OK, but who is going to be enforcing that law? I may be mistaken (and please correct me if I am), but I would assume that park rangers have no non-federal authority. The state police and local folks jurisdiction ends when you cross into federal land. If I'm technically breaking state law, do NP police have the jurisdiction (and education on that state's laws) to enforce it? Can state/local officers be "asked" by NP to come in and enforce their jurisdiction on federal land?

I'm not advocating doing this, I'm just curious how the different jurisdictions get along.

The topic of CCW in California is so complex and constantly changing that it would take a dedicated forum to even begin to comprehend them.

Luckily, one already exist.

http://calccw.com/

As with any internet forum, you need to take any information with a grain of salt, there is a lot of misinformation from people with good intentions, but who really are just repeating things they've heard from AFOAF (A friend of a friend) who's daughter's boyfriend's room-mate was told by a off duty police officer 5 years ago. Some of it might be generally correct, but some of is completely off base.

I don't have the statute or implementing regs in front of me but if it says that the park's firearm policy mirrors the federal and surrounding state-local statutes then I'd expect they could enforce it.

Would they ignore expired vehicle tags?

I wouldn't count on it.

I believe the change in national parks says that you may carry a concealed weapon in a national park ONLY IF you are in compliance with state laws. So if you are caught carrying concealed in a national park when you should not be, then they would be enforcing the federal law that says you can't carry unless authorized in the corresponding state. They would not be enforcing the underlying state law. That state law only serves as a basis to decide whether you are violating a federal law or not. At least that's the way I understand this.

You are correct in some parks, and incorrect in others. It is rather complex, and my information and understanding is rather dated. The situation varies from park to park. In a good many parks, both state and federal laws apply. Varying with the situation, some rangers are also deputy sheriffs for the local county.

Here is a thread at calguns showing advertising about a conference on your questions.

Become informed.

Hyatt SF Sept 24-26.

http://www.calguns.net/calgunforum/showthread.php?s=1cbee57047a8bc29f20493ecf83690af&t=337830

According to a friend,of whom is a US Marshall,The National Parks are controlled by The Dept. of The Interior.The Dept.of The Interior is Completely a Federal Jurisdiction,However...Any Law enforcement officer, of that state,Can Hold you in custody for 72hrs.& Confiscate any weapons,Should they deem it Necessary,As per their own Better Judgement.Even if you are found to be "Legitimate"Afterward,Getting your gun back can or Will be,A whole different case! Sounds Like a "Grand-Mal PITA" to go through,However it's Peanuts,Should the act of Defending You or your Family,Have to be carried out!Are you an NRA Member?The NRA will be your BEST Defense,should you need it!I am NOT Advocating Breaking the Law,by ANY means! I do Have Affiliation with The NRA,I am A Member!

For concealable weapons in California, I recommend hanging out at a California-specific site, like calguns.net. The laws for concealed carry in California are numerous, but they're pretty clear. It may be fun to re-invent the wheel by discussing this topic with people from other states. However, you may be wasting your time because there are definite answers for every weapon that I know.

I choose not to discuss concealed carry weapons on this site. I don't need to hear comments about my choice of weapons from people who don't know California laws. Concealed carry is not a good topic for lightweight Internet chatting. If you want to carry concealed legally, then it'll serve you well if you just get it right the first time.