Rangers F.C. policy of not signing Catholics
Between the First World War and the late 1980s, the Scottish football club Rangers had an unwritten policy not to sign any player who was a Catholic, or employ Catholics in other roles. Since the early 20th century, Rangers have been viewed as a Protestant, Unionist, anti-Catholic club, in contrast to their Old Firm rivals, Celtic, who have been seen as an Irish Catholic club, although Celtic never had a similar policy.
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