Can Trump take long-term control of Washington's police?

But Trump can expect a flurry of lawsuits if he tries to do so without Congress's approval. Here is why.

The Democratic mayor of Washington, Muriel Bowser, has authority over the city's Metropolitan Police Department. But a federal law from 1973 known as the Home Rule Act allows the president to take control of the MPD for 30 days during an emergency.

Trump invoked this provision of the Home Rule Act on Monday, saying in an executive order that there is a "crime emergency" in the city.

Bowser has pushed back on Trump's claims of unchecked violence, highlighting that violent crime hit its lowest level in more than three decades last year, according to city data.

Trump on Wednesday suggested that he could extend the 30-day federal takeover without congressional approval.

“If it’s a national emergency, we can do it without Congress, but we expect to be before Congress very quickly,” Trump said.

But legal experts said the law is clear: A presidential takeover is limited to 30 days, unless Congress votes to extend it through a joint resolution.

Any legislation to extend Trump's control over the police department would likely fail in the Senate where Democrats can use procedural rules to block most bills.

Trump has repeatedly threatened to put DC under full federal control, but that appears very unlikely.

The Home Rule Act delegated the day-to-day work of municipal government to the mayor's office and a city council. To exert full federal control of D.C., Trump would need Congress to repeal that law.

Such a repeal would require 60 votes in the U.S. Senate, where Trump's Republican Party has a 53-47 advantage. Democrats have been supportive of home rule for DC and are not expected to cross party lines to endorse Trump's vision.

Trump has broad control over the D.C. National Guard’s 2,700 soldiers and airmen. They report directly to the president, unlike counterparts in other states and territories.

Trump said on Monday he was deploying 800 National Guard troops to Washington.

Trump in recent months has also directed federal law enforcement agencies such as the FBI to increase the police presence in Washington. Trump has broad authority to reallocate federal agency personnel.

Trump has said the federalisation of Washington's police force could serve as a model for other U.S. cities. He has previously said he would expand his efforts to other Democratic-run cities such as Chicago that he claims have failed to address crime.

But Washington is unique because of the district's legal status and the Home Rule Act provision allowing for a presidential MPD takeover.

There is no similar legal authority Trump can cite to take over police departments in other cities. The Tenth Amendment vests in states a police power to provide for the health, safety, and welfare of state citizens.

Trump could decide to send the National Guard or other military to support law enforcement in other cities, as he did when he sent 4,000 National Guard troops to Los Angeles to quell protests and support federal immigration enforcement actions.

Unlike the D.C. National Guard, which reports directly to the president, each states' National Guard serves as a militia force that answers to their governors except when called into federal service.

Trump's decision to take control of the California National Guard was a break from a longstanding tradition against using the military to police civilians within the country.

California has sued the Trump administration, alleging the president improperly called the National Guard into service and violated a 19th-century law that generally prevents the military from engaging in domestic law enforcement. The president said the National Guard presence was justified because protests and acts of violence in Los Angeles were "a form of rebellion" that necessitated a military response.

A judge heard testimony this week in California's lawsuit, which ultimately seeks a ruling that would return its National Guard troops to state control and a declaration that Trump's action was illegal.