"It's against the law, you know that?" Moore said in an interview with Time magazine. "It was an act of Congress that every man stand and put their hand over their heart. That's the law."
Moore, a former chief justice of Alabama known for his controversial interpretations of the Bible, and who was twice suspended from the bench for defying judicial orders, argued that a section of the U.S. Code - 36-USC-301 - forbids professional athletes from taking a knee during the national anthem. The U.S. Code, however, is a compilation of most public laws currently in force, and is not actually the law itself. And the section that Moore was referring to does not specify legal penalties.
"It's not clear to me that 36 U.S.C. 301 was ever meant to be legally binding - it says what people 'should' do rather than what they 'shall' or 'must' do," Eugene Volokh, a law professor at the UCLA School of Law, told CBS News.
The NFL has been under intense criticism from President Donald Trump and some fans because of protests by players who have refused to stand during the anthem.
On Wednesday, league owners ended a two-day meeting without enacting a measure that would require players to stand for the national anthem prior to games. Following the meeting, NFL Commissioner Roger Goodell reiterated that the league believes its players should stand for the anthem, but the owners did not implement a rule change mandating that they do so.
New York Giants co-owner John Mara said that "most of us believe that attempting to force the players to do something that they don't want to do is not going to be effective in the long run," adding that "almost every other owner feels the same."
Colin Kaepernick, a former San Francisco 49ers quarterback, started taking a knee during the national anthem last year to protest what he saw as police brutality against unarmed black people and the oppression of minorities.
Kaepernick's gesture sparked a national debate and controversy, but Trump's remarks last month that NFL owners should fire players who take a knee fueled a simmering culture war, turning sports into a political battleground.
"Wouldn't you love to see one of these NFL owners, when somebody disrespects our flag, to say, 'Get that son of a bitch off the field right now, out. He's fired. He's fired!' " said the president during a rally in Huntsville, Ala., in late September.
Since then, players across the NFL have been engulfed in a divisive culture war with Trump, caught up in a national debate over free speech, patriotism, racial identity and cultural values.
On Wednesday, Trump again criticized the NFL for failing to ensure that its players stand during the anthem. Earlier in the day, he blasted the league for its "total disrespect for our great country" following a two-day meeting of team owners that did not enact a requirement for players to stand for the anthem.
In the interview with Time, Moore said that he endorses Trump's criticism of the NFL.
"I back the President in upholding respect for the patriotism for our country, on two grounds," he said. "One, it's respect for the law. If we don't respect the law, what kind of country are we going to have? Two, it's respect for those who have fallen and given the ultimate sacrifice. I'm surprised that no one brought this up."
And when asked what is most misunderstood about his candidacy, Moore replied, "That it's about religion. It's not religious at all. God is not religion. I believe in the sovereignty of God. It's stated clearly in our law, clearly in our history, and clearly in our faith. It's not anything I'm making up."
The Washington Post's Mark Maske contributed to his report.