In the aftermath of Tuesday’s terrorist attacks on Brussels, presidential candidate Sen. Ted Cruz (R-TX) suggested that as president he would “patrol and secure” U.S. Muslim communities.

“We will do what we can to help them fight this scourge, and redouble our efforts to make sure it does not happen here. We need to immediately halt the flow of refugees from countries with a significant al Qaida or ISIS presence. We need to empower law enforcement to patrol and secure Muslim neighborhoods before they become radicalized,” Cruz said in a statement responding to terrorist attacks in Belgium’s capital city that left at least 30 dead and 230 wounded.

In response to criticism of his plan, Cruz later asserted during an interview on CNN, “That does not mean targeting Muslims. It means targeting radical Islamic terrorism.”

Cruz didn’t elaborate on how he recommends police officials distinguish between Muslims and radical Islamic terrorists, but he did say to host Anderson Cooper, “If you have a neighborhood where there’s a high level of gang activity, the way to prevent it is you increase the law enforcement presence there and you target the gang members to get them off the streets …. I’m talking about any area where there is a higher incidence of radical Islamic terrorism.”

Jonathan A. Greenblatt, CEO of the Anti-Defamation League, condemned Cruz’s reaction in a Tuesday statement, saying, “demonizing all Muslims is a misguided and counterproductive response to the terrorist threat posed by those motivated by a radical interpretation of Islam.”

“Ordering special patrols of Muslim neighborhoods will almost certainly create an adversarial relationship between law enforcement and the communities they have sworn to protect, making those communities more vulnerable, more frightened, and often less willing to help,” Greenblatt continued.

“Profiling people based on their religion or race is blatantly unconstitutional and violates the guarantee of religious protection and religious freedom,” Hina Shamsi, director of the American Civil Liberties Union’s (ACLU) national-security project, told the Nation. “One way to look at it is to replace the word ‘Muslim’ with ‘Jewish,’ ‘Christian,’ ‘African American,’ or ‘Latino.’ What’s wrong in one context is wrong in others.”

During his appearance on CNN, Cruz cited what he deemed a “successful program” implemented under former New York Mayor Michael Bloomberg, allowing New York Police Department (NYPD) officers to monitor Muslims in the city. However, as the Huffington Post reported, New York’s program was roundly unsuccessful in identifying any terrorist threats:

The GOP presidential hopeful blamed Bloomberg’s successor, Bill de Blasio, for shuttering the program. According to The Associated Press, however, the department “never generated a lead or triggered a terrorism investigation” in the six years that it eavesdropped on conversations.

Critics of profiling based on race, ethnicity, and religion say that these programs may interfere with the rights of those they target. The NYPD’s surveillance program increased stigma against Muslims, created fear among those living in targeted communities, damaged relationships between Muslims and the police, and silenced free speech, according to an American Civil Liberties Union fact sheet.

Ibrahim Hooper, national communications director for the Council on American-Islamic Relations, warned in an interview with Vox that Cruz’s plan could go even further than the NYPD’s surveillance program.

“This goes light-years beyond that. Cruz is talking about police ‘securing’—what does that mean? Does that mean checkpoints on every corner? Does that mean papers on every street?” Hooper told the publication. “To me, this sounds like an armed occupation of Muslim neighborhoods.”