San Francisco 49ers display Black Lives Matter flag at stadium next to the American and California flags

The San Francisco 49ers flew the Black Lives Matter flag outside Levi's Stadium on Monday in support of the social justice protests that have taken place across the country since former Minneapolis Police Department officers killed George Floyd in May, NBC Sports reported.

The 49ers, which previously employed former quarterback-turned-activist Colin Kaepernick, posted a picture of the Black Lives Matter flag flying next to the American flag and the California state flag with the caption "indivisible with liberty and justice for all."

Although major American professional sports leagues are still on hiatus due to COVID-19, the recent racial unrest in the U.S. leads to questions about what role political activism will play in sports when they do return.

The most prominent and divisive sports protests in recent memory, kneeling during the national anthem, could potentially become source of debate and controversy whenever the NFL and NBA resume play. President Donald Trump recently weighed in on that issue again.

"I said 'where did that come from in the middle of the summer? Nobody's even asking,'" Trump said during his rally in Tulsa, Oklahoma, on Saturday. "We will never kneel to our national anthem or our great American flag. We will stand proud, and we will stand tall."

Trump was responding to previous comments from NFL Commissioner Roger Goodell, which seemed to suggest he was now going to be more supportive of peaceful protests in the league.

"I personally protest with you, and want to be part of the much-needed change in this country," Goodell said. "We the National Football League admit we were wrong for not listening to NFL players earlier and encourage all to speak out and peacefully protest."

The prerogative of NFL players to kneel in protest during the national anthem has been a source of conflict between the players and the league for years. Kaepernick began kneeling during the national anthem in 2016 to protest police brutality and other racial and social injustices.