Question: Rostker v. Goldberg held that the practice of what way of filling armed forces vacancies was consitutional?

Context:
2010 Kiev Victory Day Parade
The 2010 Kiev Victory Day Parade was held on May 9, 2010 in Kiev, honoring the 65th anniversary of the Soviet Union's victory in the Great Patriotic War.
 Inspecting the parade was the Chief of General Staff of the Armed Forces General of the Army Ivan Svyda.
 The commander of the Ukrainian Armed Forces, Colonel General Gennady Vorobyov, Commanded the Parade.
 The President of Ukraine Viktor Yanukovych delivered a jubilee address.
 2,500 members of the Ukrainian Armed Forces troops from Russia and Belarus took part in the parade.
 17 military orchestras took part in the parade under the command of the Chief of the Military Music Department of the General Staff of the Ukrainian Armed Forces, Major General Volodymyr Derkach.
Rostker v. Goldberg
Rostker v. Goldberg, 453 U.S. 57 (1981) , was a decision of the United States Supreme Court holding that the practice of requiring only men to register for the draft was constitutional.
 After extensive hearings, floor debate and committee sessions on the matter, the United States Congress enacted the law, as it had previously been, to apply to men only.
 Several attorneys, including Robert L. Goldberg, subsequently challenged the gender distinction as unconstitutional.
 (The named defendant is Bernard D. Rostker, Director of the Selective Service System.)
 In a 6-3 decision, the Supreme Court held that this gender distinction was not a violation of the equal protection component of the due process clause, and that the Act would stand as passed.
One Rank, One Pension
One Rank One Pension (OROP), or "same pension, for same rank, for same length of service, irrespective of the date of retirement", is a longstanding demand of the Indian armed forces and veterans.
 The demand for pay-pension equity, which underlies the OROP concept, was provoked by the exparte decision by the Indira Gandhi-led Indian National Congress (INC) government, in 1973, two years after the historic victory in the 1971 Bangladesh war, and shortly after Field Marshal SHFJ Manekshaw retired, to decrease armed forces pensions by 20–40 percent, and increase civilian pensions by 20 percent, without consultation with armed forces headquarters.
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Chief of the Defence Staff (Canada)
The Chief of the Defence Staff (CDS; French: "chef d'état-major de la Défense" ) is the second most senior member of the Canadian Armed Forces (after the commander-in-chief) and heads the Armed Forces Council, having primary responsibility for command, control, and administration of the forces, as well as military strategy, plans, and requirements.
 The position is held by a senior member of one of the three main branches of the Canadian Armed Forces.
 The current CDS, since 17 July 2015, is Jonathan Vance.
September 16 military parade
The 16 September military parade in honour of the anniversary of Mexican Independence is an annual tradition dating back to the late 19th century and the beginning of the professionalisation of the Mexican Armed Forces in the 20th century.
 Held yearly in the Zócalo in Mexico City, this parade, the largest of the various parades held simultaneously nationwide on September 16, Mexican Independence Day, is presided by the President of Mexico in the fulfillment of his duty as the Supreme Commander of the Armed Forces.
 It is also attended by members of the Cabinet of Mexico, the Congress of the Union, civil service employees, the Secretaries of National Defense and Navy, members of the Mexican Armed Forces and Federal Police, uniformed service veterans, the state diplomatic corps, delegations representing the religious sector, indigenous peoples, sports and the private sector, and the general public.
 Seen on TV and the Internet and heard on radio, this is one of the biggest events of the year.
 Taking part in this are members of the Mexican Armed Forces and the Federal Police.
Fernando Tapias Stahelin
Fernando Tapias Stahelin (born July 14, 1943 - † September 27, 2015) was a General (retired) of Colombian Armed Forces.
 He served as Chairman of the Joint Chiefs of Staff of Colombian Armed Forces for a period of four years (1998–2002) during the presidential term of president Andres Pastrana.
 After that, he served as ambassador of Colombia in Dominican Republic from 2002 to 2004 and subsequently served as Deputy Minister of Defense for its social and business group for two years from 2009 to 2010 during the presidential term of president Alvaro Uribe.
 He was in the Colombian Armed Forces for 41 years, achieving all the military ranks all the way up to his appointment as General Commander for the Colombian Armed Forces.
Conscription in the United States
Conscription in the United States, commonly known as the draft, has been employed by the federal government of the United States in four conflicts: the American Civil War, World War I, World War II, and the Cold War (including both the Korean and Vietnam Wars).
 The third incarnation of the draft came into being in 1940 through the Selective Training and Service Act.
 It was the country's first peacetime draft.
 From 1940 until 1973, during both peacetime and periods of conflict, men were drafted to fill vacancies in the United States Armed Forces that could not be filled through voluntary means.
 The draft was ended when the United States Armed Forces moved to an all-volunteer military force.
 However, the Selective Service System remains in place as a contingency plan; all male civilians between the ages of 18 and 25 are required to register so that a draft can be readily resumed if needed.
Armed Forces Covenant
The Military Covenant or Armed Forces Covenant is a term introduced in 2000 into British public life to refer to the mutual obligations between the nation and its Armed Forces.
 According to "The Guardian", "it is an informal understanding, rather than a legally enforceable deal, but it is nevertheless treated with great seriousness within the services".
 It was coined in , and has now entered political discourse as a way of measuring whether the government and society at large have kept to their obligations to support members of the armed forces.
Armed Forces Day (Poland)
Armed Forces Day, known also as the Feast of the Polish Armed Forces (Polish: "Święto Wojska Polskiego" ), is a national holiday celebrated annually on 15 August in Poland, commemorating the anniversary of the 1920 victory over Soviet Russia at the Battle of Warsaw during the Polish–Soviet War.
 Armed Forces Day is held in conjunction with the Day of the Assumption of the Virgin Mary, itself a separate public holiday.
 The event is marked by military parades, equipment reviews, showcases and remembrances by all branches of the Polish Armed Forces across the country.
 One of the most prominent events of the day is in the capital Warsaw, which hosts a large military parade through the city's center.
 Originally celebrated during the Second Republic, the holiday was barred by authorities during the communist era beginning in 1947, only to be revived again in 1992.
Franklin D. Roosevelt's record on civil rights
In June 1941, Roosevelt issued Executive Order 8802, which created the Fair Employment Practice Committee (FEPC).
 It was the most important federal move in support of the rights of African-Americans between Reconstruction and the Civil Rights Act of 1964.
 The President's order stated that the federal government would not hire any person based on their race, color, creed, or national origin.
 The FEPC enforced the order to ban discriminatory hiring within the federal government and in corporations that received federal contracts.
 Millions of blacks and women achieved better jobs and better pay as a result.
 The war brought the race issue to the forefront.
 The Army and Navy had been segregated since the Civil War.
 But by 1940, the African-American vote had largely shifted from Republican to Democrat, and African-American leaders like Walter Francis White of the NAACP and T. Arnold Hill of the Urban League had become recognized as part of the Roosevelt coalition.
 In June 1941, at the urging of A. Philip Randolph, the leading African-American trade unionist, Roosevelt signed an executive order establishing the Fair Employment Practice Committee and prohibiting discrimination by any government agency, including the armed forces.
 In practice the services, particularly the Navy and the Marines, found ways to evade this order — the Marine Corps remained all-white until 1942.
 In September 1942, at Eleanor's instigation, Roosevelt met with a delegation of African-American leaders, who demanded full integration into the forces, including the right to serve in combat roles and in the Navy, the Marine Corps and the United States Army Air Forces.
 Roosevelt agreed, but then did nothing to implement his promise.
 It was left to his successor, Harry S. Truman, to fully desegregate the armed forces.

Answer: Conscription