—to this: "The state is under no duty to make school buildings available for public meetings.*** If it elects to do so, however, it cannot arbitrarily prevent any members of the public from holding such meetings [nor]*** make the privilege of holding them dependent on conditions that would deprive any members of the public of their constitutional rights. A state is without power …

We explained that while "[t] he state is under no duty to make school buildings available for public meetings

—"... the state need not open the doors of a school building as a forum and may at any time choose to close them. Once it opens the doors, however, it cannot demand tickets of admission in the form of convictions and affiliations that it deems acceptable."

Striking the part of the ordinance that we have held to be unconstitutional does not "vitiate the whole act

If it is unconstitutional to restrain plaintiff from advocating overthrow of the government, it is a fortiori unconstitutional to require it to prove or declare that it does not advocate overthrow of the government

" `[U] nconstitutional provisions will not vitiate the whole act, unless they enter so entirely into the scope and design of the law, that it would be impossible to maintain it without such obnoxious provisions

The issue is the extent of the Board's control over who will, and will not, speak once it has invited, as part of its educational program, student groups to arrange discussions of controversial subjects by guest speakers.[2] Once the Board has opened a forum for the free expression of ideas, it may not exceed constitutional limitations in picking the ideas it wishes to be freely …

The remaining parts of the statute may be preserved if they can be separated from the unconstitutional part without destroying the statutory scheme or purpose

—it is settled that a person cannot properly be barred or removed from public employment arbitrarily or in disregard of his constitutional rights