An Arizona police chief who calls himself “America’s Toughest Sheriff” sued Barack Obama on Thursday soon after the U.S. president imposed sweeping immigration reforms, saying the changes were unconstitutional.

Maricopa County Sheriff Joe Arpaio, whose force used racial profiling during a crackdown on illegal migrants last year according to a judge, said Obama has overstepped his powers by bypassing Congress and bringing in the changes himself.

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Arpaio’s lawsuit said the reforms, which eased the threat of deportation for about 4.7 million undocumented immigrants, amounted to an amnesty and would encourage more people to cross the border illegally.

The biggest overhaul to immigration in a generation has set up a confrontation between the president and Republicans, who took full control of Congress this month and also said the president had gone too far by imposing the changes.

It was Obama’s biggest use of executive actions in a year in which they have become his signature way of working around congressional gridlock.

“(Obama’s immigration) programs are unconstitutional abuses of the President’s role in our nation’s constitutional architecture and exceed the powers of the President within the U.S. Constitution,” read Arpaio’s complaint filed in a federal court in Washington.

Obama earlier dismissed Republican accusations that the changes amounted to an amnesty for illegal immigrants.

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“Amnesty is the immigration system we have today, millions of people who live here without paying their taxes or playing by the rules,” Obama said.

The White House could not be immediately reached for comment on the lawsuit.

An Arizona federal judge May 2013 ruled that deputies of Arpaio’s office had racially profiled Latino drivers.

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The judge ordered that race no longer be used as a factor in law enforcement decisions and appointed a court monitor to oversee Arpaio’s operations.

Arpaio has denied that racial profiling occurred and has appealed against the judge’s ruling.

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(Reporting by Curtis Skinner in San Francisco; Additional reporting by David Schwartz in Phoenix; Editing by Andrew Heavens)