If that court concludes that the Dane County circuit court was wrong - a conclusion that is highly likely - then any new contract that violates Act 10 will be unlawful and presumably void.
Moreover, the fact that a single circuit court judge in Madison thinks the Act is unconstitutional will have exactly no impact on the deliberation of higher courts. Lower court decisions are entitled to deference when they involve factual findings or the exercise of discretion. The decision holding Act 10 to be unconstitutional involved neither and is subjected, as lawyers like to say, to de novo
Negotiating a new contract would be even more problematic than that. The attorney for the plaintiffs in the Dane County case seems to think that a municipality that does not agree to negotiate terms that are forbidden by Act 10 would be engaged in an unfair labor practice. In his view, the Wisconsin Employment Relations Commission - to whom such charges are initially directed - would be bound by the circuit court decision because its members were defendants in the case.
But there are at least two problems with his argument. First, it us unclear that WERC, in its capacity as a tribunal, can be bound by a declaratory judgment in adjudicating the rights of a party who is not itself bound by that judgment. For example, if the Mequon-Thiensville School District is charged with an unfair labor practice for complying with Act 10, it was not a party to the case finding it to be unconstitutional. The question is one that only a civil procedure professor (and I've been one of those) could love.
But there is a more fundamental problem. WERC's decisions are not final. They may be reviewed by a circuit court. That court will not be bound by the Dane County decision which - and this is black letter law - has no precedential value. A reviewing court need not follow it.
The future of Act 10 will be decided by the Wisconsin Supreme Court. If, as I think is almost certain to happen, the law is upheld then entering into agreements that are not permitted by it will create one hot mess. It will invite s a lawsuit in the short run and, in all likelihood, a tangled set of illegal obligations and payments to undo in the longer run.
Cross posted at Purple Wisconsin.