President Donald Trump announced on Wednesday a new travel ban affecting citizens from 12 countries, with additional restrictions on travelers from seven others.

The ban will take effect Monday at 12:01 a.m., giving advance notice to avoid the airport disruptions seen in 2017.

This time, the policy has stronger legal backing following a Supreme Court ruling.

The 12 countries included in the ban are Afghanistan, Myanmar, Chad, the Republic of Congo, Equatorial Guinea, Eritrea, Haiti, Iran, Libya, Somalia, Sudan, and Yemen.

Visitors from Burundi, Cuba, Laos, Sierra Leone, Togo, Turkmenistan, and Venezuela will face heightened restrictions.

In a social media video, Trump linked the new ban to Sunday’s terror attack in Boulder, Colorado, saying it highlighted the risks posed by some visitors who overstay their visas.

The suspect, from Egypt—a country not on the restricted list—was reported by the Department of Homeland Security to have overstayed a tourist visa.

Trump stated that some countries have poor screening and vetting systems or have a history of refusing to repatriate their citizens.

His conclusions are mainly drawn from an annual Homeland Security report that tracks visa overstays by tourists, business travelers, and students arriving by air and sea, focusing on countries with high rates of people staying after their visas expire.

“We don’t want them,” Trump said.

The addition of Afghanistan to the ban upset some supporters who have been helping with resettlement efforts.

However, Afghans with Special Immigrant Visas—typically those who worked closely with the U.S. during the two-decade war—are exempt from the restrictions.