SAO PAULO, June 17 (Reuters) - A judge in Brazil has overturned an appeal ruling and decided to reinstate permission for steelmaker CSN to make appointments to the board of rival Usiminas, in which CSN has a stake.

The ruling on Thursday by judge Luciana Moura, which was published on the court's website, came just 24 hours after an appeals judge had blocked the original decision by the country's antitrust authority Cade to allow CSN appointees to Usiminas' board.

The case, one of several connected to Cade's decision, is another chapter in a shareholder battle for control of the Usiminas boardroom that has increasingly moved into the courts.

Controlling shareholders Nippon Steel & Sumitomo Metal Corp and Techint have been at loggerheads for nearly two years, while CSN, which owns a significant stake but is outside the controlling group, is exerting increasing influence.

CSN, formally known as Companhia Siderúrgica Nacional SA, owns 19 percent of Usiminas preferred shares and 10 percent of its common shares, according to Thomson Reuters data.

(Reporting by Alberto Alerigi)