An Appeals Court ruled Friday that the National Labor Relations Board overstepped its authority when it announced a rule requiring all workplaces to prominently display a poster explaining employee union rights. It was the second Appeals Court to strike down the rule this year.

The NLRB’s ruling, first made two years ago, required most workplaces to include a poster prominently explaining workers’ rights under the National Labor Relations Act. If they did not that itself constituted an unfair labor practice by the business, the board said.

Big Business has pushed back against the ruling and won a series of court battles over it. The DC Circuit Court of Appeals  in March vacated the NLRB’s rule. On Friday, the Fourth Circuit Court of Appeals also tossed out the rule in a case brought against it by the Chamber of Commerce.

The Friday ruling said the NLRB’s authority:

[O]nly empowers the Board to carry out its statutorily defined reactive roles in addressing unfair labor practice charges and conducting representation elections upon request. Indeed, there is no function or responsibility of the Board not predicated upon the filing of an unfair labor practice charge or a representation petition.

This ruling goes further than the prior Appeals Court. It calls into question the NLRB’s authority to promulgate rules not explicitly cited in the NLRA, a serious blow to the board.

The NLRB has come under considerable fire under during the Obama administration for its aggressive, pro-union rulemaking. It currently lacks a valid quorum to act though, a consequence of President Obama using recess appointments to fill the five-member board. A current slate of five nominees is awaiting a Senate vote but Republicans are unlikely to allow one at least until a potential Supreme Court ruling on the validity of Obama’s appointees.