"Please don't be too nice," he said to the audience in Long Island, New York.
While the speech was largely focused on the fight against the gang MS-13, it appeared that Trump was directing his comments about police interactions with suspected criminals in general.
He described the precautions typically taken by police where they place a hand over a suspect's head while they're being put into a police car to protect them.
"When you see these thugs being thrown into the back of a paddy wagon, you just seen them thrown in, rough. I said, ‘Please don’t be too nice,’" he said.
"When you guys put somebody in the car and you’re protecting their head you know, the way you put their hand over [their head]," Trump continued, mimicking the motion. "Like, 'Don’t hit their head and they’ve just killed somebody, don’t hit their head.' I said, 'You can take the hand away, OK?'
"I have to tell you, you know, the laws are so horrendously stacked against us, because for years and years, they've been made to protect the criminal. Totally made to protect the criminal. Not the officers. You do something wrong, you're in more jeopardy than they are," he added.
"I can tell you, I saw some photos where [acting ICE Director] Tom [Homan]'s guys, rough guys, they're rough, I don't want to ... say it because they'll say that's not politically correct, you're not allowed to have rough people doing this kind of work. ... Just like they don't want to have rich people at the head of treasury," Trump said.
The Suffolk County Police Department, the county in which Trump spoke, tweeted about its policy on handling prisoners -- although it did not specifically cite the president.
"The SCPD has strict rules & procedures relating to the handling of prisoners," it tweeted following the president's speech. "Violations of those rules are treated extremely seriously."
A subsequent tweet read, "As a department, we do not and will not tolerate roughing up of prisoners."
The American Civil Liberties Union also responded, condemning the president’s remarks.
“Innocent until proven guilty? Our president would rather not bother with that, expanding the role of the police officer to include judge, jury, and executioner,” he said.
This isn't the first time that Trump has seemingly condoned physicality.
"If you see somebody getting ready to throw a tomato, knock the crap out of them, would you? Seriously, OK? Just knock the hell ... I promise you I will pay for the legal fees. I promise, I promise," he said on Feb. 1, 2016.
At a Las Vegas rally later that month, he said security guards were too gentle with a protester. "He's walking out with big high-fives, smiling, laughing," Trump said. "I'd like to punch him in the face, I'll tell you."
A similar situation unfolded at a rally that month in Warren, Michigan.
"Get him out," he said of a protester. "Try not to hurt him. If you do, I'll defend you in court. Don't worry about it."