WASHINGTON — Driven either by principle or political expediency, President Barack Obama is working to build and maintain a powerful presidency that pushes the edge of what it can do, while often telling Congress and the courts to mind their own business.

In the last week alone, he refused a subpoena to share Justice Department emails with Congress, told courts he doesn’t have to justify his claimed power to assassinate suspected terrorists and decided to stop deporting certain illegal immigrants even though Congress has refused to enact a law to do that.

Those moves cap a slow buildup of executive branch power since Obama took office in January 2009. Some actions build on war powers seized by the administration of President George W. Bush and Vice President Dick Cheney. Some assert new domestic authority.

Taken together, they reinforce the strengthening presidential power that Cheney pursued ever since he served as White House chief of staff to Gerald Ford and watched Congress take power away from a presidency weakened by Vietnam and Watergate.

“Particularly with regard to national security powers, Obama is as vigorous in exercising those powers, and expanding some of them, as his predecessor,” said Gene Healy, the author of the book “The Cult of the Presidency: America’s Dangerous Devotion to Executive Power.”

At the White House, press secretary Jay Carney spoke Thursday of separation of powers rather than checks and balances, casting the decision to shield the Justice Department as part of the broader principle of presidential authority.

“It is his responsibility as steward of the executive branch to retain the capacity of this administration and every administration going forward to function appropriately and independently from the congressional branch of government,” Carney said.

“The assertion of privilege has to do with the absolute necessity of retaining the executive branch’s independence enshrined in the Constitution in the separation of powers to allow it to appropriately and independently … deliberate and respond to these kinds of inquiries.”

Obama started out more skeptical.

In 2007, as a candidate, he criticized Bush for using executive privilege to shield aide Karl Rove from congressional questions about politics in the Justice Department.

“There’s been a tendency on the part of this administration to try to hide behind executive privilege every time there’s something a little shaky that’s taking place,” he said then. “There doesn’t seem to be any national security issues involved. … I think the American people deserve to know what was going on there.”

Last week, Obama asserted executive privilege to shield the Justice Department from a subpoena for emails, part of a congressional investigation into a possible political cover-up in the wake of the Fast and Furious gun scandal.

Last year, he rejected pressure to stop deporting the children of illegal immigrants, noting that Congress hadn’t yet approved the proposed DREAM Act, which would allow him to do that.

“Sometimes when I talk to immigration advocates, they wish I could just bypass Congress and change the law myself,” he said in Texas in May 2011. “But that’s not how a democracy works. What we really need to do is to keep up the fight to pass genuine, comprehensive reform. That is the ultimate solution to this problem.”

On June 15, his administration announced that it would use prosecutorial discretion to stop the deportations of those young illegal immigrants.

Last week, his administration argued in a late-night court filing that it shouldn’t be required to reveal anything about its policy of targeting suspected terrorists abroad for death by drones, even if they’re U.S. citizens.

“We continue to have profound concerns with the power the administration is claiming and with the proposition that the president should be permitted to exercise this power without oversight by the courts,” said Jameel Jaffer, the deputy legal director of the American Civil Liberties Union.

“That the administration believes a power so sweeping should be exercised in secret is astounding.”