Yes, you could. I did, several times, and no one ever arrested me or anything. However, there came a time when they worried about too many nutcases wanting to take a hammer to it (this actually happened
) so they restricted access to formal occasions. And then, of course, the National Constitution Center was built at great taxpayer expense to house the Bell behind a bulletproof glass partition.
Classic case of a few bad apples ruining it for everybody.