History buffs probing the origins of the Cross of St. George will find themselves exploring a labyrinth of faith and legend in the Late Middle Ages.

But to see this heraldry symbol, just look at England's flag -- a bright red cross on a white background. Soccer fans may notice that the English side's 2018 World Cup kits feature a St. George's Cross on the back collar. During "away" games, a subtle cross covers the entire front of the red jersey.

This is interesting, since the International Football Association Board's "Laws of the Game" -- used at the FIFA World Cup -- state: "Equipment must not have any political, religious or personal slogans, statements or images." This rule "applies to all equipment (including clothing) worn by players," according to IFAB guidelines.

Does this apply to religious symbols woven into the flags and traditions of many nations?

"It's important to remember that the rules of soccer came from Europe," said Jennifer Bryson, director of the Islam and Religious Freedom office at the Religious Freedom Institute in Washington, D.C. "The IFAB began in England. FIFA began in Europe. Both of these organizations are supposed to be truly international -- but their roots are European.

"Basically, the word 'religion' in these rules means 'Christianity.' … FIFA is still trying to come to terms with the rest of the world."

It's hard to imagine a more challenging task than imposing modern European secularism on this very religious planet, said Bryson, in a telephone interview. England's Cross of St. George is just one example of faith mixing with football. Players from Iran wear their nation's flag, with a red "Allah" symbol and two bold horizontal bars consisting of 11 repetitions of "Allahu akbar (God is greatest)." Can Brazilian evangelicals keep wearing "I belong to Jesus" t-shirts under their jerseys?

Bryson has paid close attention during World Cup 2018, looking for expressions of religious faith. She summarized her early findings in a late June lecture in Washington entitled "Exorcisms and Exercise, Crosses and Cross Passes: What the World Cup has to do with Religious Freedom."