Occasionally I run across some Websites, blogs, etc. where the person not only brags about taking their pet hiking to Mt. Rainier NP, but sometimes these people show photos of their pet on trails and other places pets where aren't allowed or without a leash.
Remember folks, pets should not be taken to Mt. Rainier NP because of the narrow restrictions on pets and the ban on taking them on trails, outside of campgrounds and visitors facilities, and always on a leash. You can only take pets on a leash in parking lots, picnic areas, campgrounds and along highway (turnouts). This means when you're anywhere else, pets must be in vehicles.
I've run across hikers and visitors with pets, all dogs of course, walking around the NP like it's their neighborhood, and every time I remind them it's illegal and not appreciated by other visitors and hikers. And consider if the pet ran off hiking on a trail or elsewhere, would you be able to find them before they become completely separated and lost from you.
Remember it's not about you having your pet with you, and what you think the pet enjoys being outside in the NP. It doesn't matter how well trained your pet. It doesn't matter how important your pet is to you. It doesn't matter your pet makes a great hiking companion. It doesn't matter you take your pet hiking everywhere else in the Cascade Mountains outside National Parks.
It doesn't matter. Read and follow the rules on pets. And better yet, leave them at home.