Federal agents face off against protesters in Portland, Ore.

PORTLAND, Ore. — Federal law enforcement officers’ actions at protests in Oregon’s largest city, conducted without local authorities’ consent, are raising the prospect of a constitutional crisis — one that could escalate as weeks of demonstrations find renewed focus amid clashes with camouflaged, unidentified agents outside Portland’s U.S. courthouse.

A protester gestures in front of federal police personnel in Portland, Ore., as protests continue across the United States.

(AFP )

A demonstrator shouts slogans using a bullhorn next to a group of military veterans during a Black Lives Matter protest at the Mark O. Hatfield United States Courthouse in Portland.

(Marcio Jose Sanchez/Associated Press)

Federal officers advance on protesters during a Black Lives Matter demonstration at the Mark O. Hatfield U.S. Courthouse in Portland, Ore.

(Marcio Jose Sanchez/Associated Press)

Demonstrators use leaf blowers to try to blow back tear gas launched by federal officers during a Black Lives Matter protest at the Mark O. Hatfield United States Courthouse in Portland, Ore.

(Marcio Jose Sanchez/Associated Press)

Demonstrators sit and kneel as tear gas fills the air during a Black Lives Matter protest at the Mark O. Hatfield United States Courthouse in Portland, Ore.

(Marcio Jose Sanchez/Associated Press)

A demonstrator plays a trumpet from atop a steel fence during a Black Lives Matter protest at the Mark O. Hatfield United States Courthouse in Portland, Ore.

(Marcio Jose Sanchez/Associated Press)

A demonstrator speaks to a crowd from the bed of a pickup truck during a Black Lives Matter protest at the Mark O. Hatfield United States Courthouse in Portland, Ore.

(Marcio Jose Sanchez/Associated Press)

A demonstrator argues with a federal officer during a Black Lives Matter protest at the Mark O. Hatfield United States Courthouse in Portland, Ore.

(Marcio Jose Sanchez/Associated Press)

Protestors carry umbrellas as they gather at the Mark O. Hatfield Courthouse in Portland, Ore.

(AFP)

Federal officers walk through tear gas while dispersing a crowd of about 1,000 people during a protest at Mark O. Hatfield U.S. Courthouse in Portland, Ore.

(Nathan Howard/Getty Images)

A protester escapes a federal officer during an arrest attempt in front of the Mark O. Hatfield U.S. Courthouse in Portland, Ore.

(Nathan Howard/Getty Images)

Hundreds of protesters hold their phones aloft on Monday in Portland, Ore.

(Noah Berger / Associated Press)

A federal officer pepper-sprays a protester in front of the federal courthouse in Portland, Ore., on Monday.

(Nathan Howard / Getty Images)

Portland demonstrators on Monday.

(Nathan Howard / Getty Images)

Federal agents use crowd-control munitions to disperse protesters on Sunday.

(Noah Berger / Associated Press)

Protesters flee through tear gas.

( Nathan Howard / Getty Images)

Federal officers on the streets of Portland on Tuesday.

(Noah Berger / Associated Press)

Police walk through fire and smoke in Portland.

(Dave Killen / Oregonian)

A protester walks past a line of federal officers on Tuesday.

(Nathan Howard / Getty Images)

Tear gas in Portland.

(Dave Killen / Oregonian )

Police respond to protesters.

(Dave Killen / Oregonian )

A police officer is silhouetted near a burning car.

(Mark Graves / Oregonian)

Outside the federal courthouse in Portland on Monday.

(Nathan Howard / Getty Images)

A federal officer points to a protester while clearing the street in front of the federal courthouse.

(Nathan Howard / Getty Images)

Federal agents try to disperse protesters.

(Noah Berger / Associated Press)

Protesters outside a police station in Portland.

(Sean Meagher / Oregonian )

Federal officers and a protester carrying an American flag face off.

(Nathan Howard / Getty Images)

Federal agents and tear gas.

(Dave Killen / Oregonian)

A protester waves an American flag.

(Nathan Howard / Getty Images)

Federal officers stand guard.

(Nathan Howard / Getty Images)