Complex sentence: The employer has the right under the First Amendment to express its support for or opposition to unionization, so long as it does not threaten reprisals or promise benefits to its employees contingent on the outcome of the election.
Split into simpler sentences: The employer has the right under the First Amendment to express its support for or opposition to unionization. The permissible expression must not threaten reprisals or promise employee benefits contingent on the outcome of the election.