April 28, 1788: Maryland becomes 7th state to ratify the Constitution

Maryland was one of the 13 original colonies to revolt against British rule in the Revolutionary War. In 1781, Maryland was the 13th state to approve the ratification of the Articles of Confederation, which brought the U.S. into being as a united, sovereign and national state. It 1788, Maryland was the seventh state admitted to the Union after ratifying the Constitution.

April 27, 1950: South Africa passes Group Areas Act, formally segregating races and beginning era of apartheid

The Group Areas Act of 1950 was created by the apartheid government of South Africa and assigned racial groups to different residential and business sections in urban areas. An effect of the law was to prevent nonwhites from living in the most developed areas. The law led to the forced removal of nonwhites from homes located in areas designated for whites. The act was repealed 41 years later on June 5, 1991.

Apartheid was a system of legalized racial segregation enforced by the South African government between 1948 and 1994. Apartheid was dismantled from 1990 to 1993.

April 26, 2001: World Intellectual Property Day established

World Intellectual Property Day, observed annually on April 26, was established in 2001 by the World Intellectual Property Organization to raise awareness of the role of intellectual property and to recognize the contribution that inventors and artists have made to the development of societies. The organization chose April 26 because it was the date on which the convention establishing the World Intellectual Property Organization began in 1970. Observance is intended to promote and expand intellectual property protection, urge countries to publicize intellectual property protection laws, increase public awareness of intellectual property rights and strengthen international exchange in the intellectual property field.

April 25, 1938: Supreme Court overturns century of federal case law in Erie Railroad Co. v. Tompkins

In Erie Railroad Co. v. Tompkins, 304 U.S. 64 (1938), the Supreme Court held that federal courts must apply state law when hearing state law claims under diversity jurisdiction. ''Diversity jurisdiction'' refers to the ability of a federal court to hear civil claims brought under state law where the parties are citizens of different states. This ruling overturned almost a century of federal civil procedure law and established the modern law of diversity jurisdiction for U.S. federal courts.

April 24, 1996: Antiterrorism and Effective Death Penalty Act of 1996 introduced

The Antiterrorism and Effective Death Penalty Act of 1996 is a law to ''deter terrorism, provide justice for victims and to provide for an effective death penalty.'' It was passed with bipartisan support by Congress after the Oklahoma City bombing.

The act had a tremendous impact on the law of habeas corpus (a legal action or writ through which detainees seek relief from unlawful imprisonment). One provision limits the power of federal judges to grant relief to a detainee unless a lower court's decision incorrectly interpreted federal law or was based on an unreasonable interpretation of the facts given the evidence.

Other provisions of the act created new law. Before the act, detainees could bring new claims through multiple habeas petitions. The act placed a bar on most second or successive petitions, and detainees are now barred from bringing successive claims in federal habeas hearings.