With President Obama set to announce his executive action on immigration tonight, GOP leaders are widely accusing him of acting like an “emperor” rather than a president, describing his plan as “lawless” and “unconstitutional” and suggesting they may respond with another government shutdown if he acts as planned.

But executive action on immigration legislation is not at all without precedent. In fact, every single president in office since the Immigration and Nationality Act was passed in 1952 (11 in total, from Eisenhower to Obama) has taken some form of immigration-related executive action. And, the Center for American Progress reports, there have been 39 such instances since 1956.

These actions have ranged from having an effect on few – such as George Bush Sr.’s granting of deferred deportation to 2,227 evacuees from the Persian Gulf who were transported to the US after the Kuwaiti invasion in 1990 – to impacting the lives of many undocumented – such as Bush Sr.’s earlier decision to offer deferred deportation to the 1.5 million undocumented children and spouses of immigrants legalized under the 1986 Immigration Reform and Control Act.

Other executive actions of note include Eisenhower’s granting of Parole to 31,915 Hungarians who escaped to the US following a failed uprising against the Soviets; Reagan’s direction that up to 200,000 Nicaraguans should be saved from deportation and granted work permits; Bush Jr.’s order to expedite naturalization for green card holders who enlisted in the military; and Obama’s deferred action for childhood arrivals (DACA).

Despite the current cries of “unconstitutionality” from Republican leaders in Congress, it is within the executive branch’s authority to decide how laws on immigration are enforced. As MSNBC reports, a group of over 100 lawyers specializing in immigration signed a joint memo earlier this year stating that the action would be a legal, constitutional move on Obama’s part, on the foundation of prosecutorial discretion.

They wrote, “The application of prosecutorial discretion to individuals or groups is grounded in the Constitution, and has been part of the immigration system for many years. Furthermore, court decisions, the immigration statute, regulations and policy guidance have recognized prosecutorial discretion dating back to at least the 1970s.”

This, they noted, has also been reinforced by the Supreme Court. “Notably, in 2012, the U.S. Supreme Court reiterated: ‘A principal feature of the removal system is the broad discretion exercised by immigration officials … Federal officials, as an initial matter, must decide whether it makes sense to pursue removal at all…’”

Conservative critics maintain that what separates Obama’s plans (the details of which still have yet to be fully disclosed) from those of his predecessors is that they do not build upon laws recently passed by Congress.

However, the Obama administration has presented the executive action as the logical follow up to S.744, the comprehensive immigration reform bill that passed through the Senate with bi-partisan support in June 2013, but which Republican House Speaker John Boehner has refused to present for vote in the House of Representatives.

Senate Majority Leader Harry Reid argued Wednesday in the Senate that House Republicans have had 510 days to act on immigration reform and have failed to do so, leaving the president with limited options.

“We’ve given them time — 510 days to be exact,” he said, according to The Hill. “They need to do comprehensive immigration reform, and they’ve refused to do just that.

“Executive action is important, but it’s not a substitute for legislation, and the Speaker should know that,” Reid said.