SYDNEY (Reuters) - Australia s High Court on Friday said nationalist politician and senator Malcolm Roberts was a citizen of Britain at the time of his nomination to parliament s upper house. Australia s parliament has been rocked by revelations that seven politicians, three ministers among them, are dual citizens, potentially ruling them ineligible to hold elected office. Friday s ruling means that the parliamentary fate of Roberts, like that of his counterparts with dual citizenships at the time of their election, will be decided next month by the high court. Even if the One Nation senator is forced to step down, however, the ruling coalition will be unaffected, since the government does not control the Senate.   I find that Senator Roberts was a citizen of the United Kingdom by descent at the time of his nomination,  Justice Patrick Keane said in his findings on the High Court website. Reuters  telephone calls to Roberts to seek comment went unanswered. A 116-year-old law requires elected lawmakers to hold only Australian citizenship.  But some politicians have discovered they hold dual citizenship by descent from a father born in another country, with a few born overseas, while one prominent lawmaker has said his mother obtained Italian citizenship on his behalf.   