The First Amendment is under assault in Arizona today...
Blocking the street, lying down in the street, chaining one's self to a rail, none of these are First Amendment protected activities. The First Amendment is not understood as protecting any and all acts so long as one can spin a tale claiming that they are a mode of expression.
"Civil disobedience" in particular is not usually protected by the First Amendment--unless it is disobedience of an official who is infringing First Amendment-protected activity. Civil disobedience is by definition the defiance of legal authority and inherently involves breaking statutory or common law.
What we are seeing from protesters today barely qualifies as civil disobedience. It's more a bully tactic than anything else. Incapable of expressing themselves in a responsible fashion (e.g. in writing) or of legitimately attracting the attention of the press, and perhaps ideologically opposed to (horror of horrors) buying advertising time or space they instead attract attention to themselves through disruption. Some are likely doing it as a "macho" thing. Next to mixing passable Lemon Drops and Cosmopolitans, few things make college-age panties drop faster than "Gee, aren't I the stud. I got arrested 'protesting against injustice'".
This bullying/posturing activity is, from a semiotic point of view, quite far from the civil disobedience of Thoreau, of Ghandi, and of SNCC and other 'Civil Rights' groups. Thoreau quite nearly defined the practice as forcing the authorities to shame themselves enforcing an unjust law. Lunch-counter sit-ins perhaps epitomized this: forcing the authorities to brutalize peaceful people to enforce the trespassing laws that made segregation possible. And the marches and blockades of Ghandi and King were no mere disruption, no mere bullying, and not in any way tantrums: they were demonstrations of the humanity of people treated as an underclass.
Every illegal immigrant engages in an act of civil disobedience when he crosses the border, when he goes to work without a visa, and when he fights to stay here. Ask "Why is that man (or woman) being taken away from his livelihood and community?" and the State is left to answer "He doesn't have the required permission slip. We don't issue those."
The "civil disobedience" we saw today, that has become a ritual on the far left, a rite of passage and perhaps one way young would-be radicals get laid, is a shameful mockery of the semiotically meaningful civil disobedience of the past and of the everyday civil disobedience of the illegal immigrant. And to assert that it is protected by the First Amendment when the point of civil disobedience is to demonstrate the injustice of a law is simply a sick joke.