- Constitutionality of President Trump's actions will likely be decided by Supreme Court
- A lone justice can tip the balance on civil rights, law and corporate regulation
(CNN)On Tuesday night, US President Donald Trump revealed his nominee for the Supreme Court.
Neil Gorsuch, a 49-year-old federal appellate judge from Colorado, is Trump's pick to replace conservative Justice Antonin Scalia, who died suddenly last year.
Gorsuch will likely face a blistering confirmation battle as Senate Democrats prepare to potentially filibuster Trump's nomination in the wake of successful Republican obstruction of President Obama's nominee last year.
While the Supreme Court usually rules on domestic issues of national importance, some cases -- such as the 2000 Bush v. Gore decision on the rightful winner of the US election -- can have huge international ramifications.
The court may be asked to rule in the near future on Trump's hugely controversial immigration ban which affects millions of people from Muslim-majority countries.
Who checks the actions of the president?
If the controversies of Trump's nascent presidency are any indication, the nation's federal courts will be busy attempting to resolve future legal disputes and the constitutionality of Trump's sweeping actions.
"That will put the Supreme Court, and potentially this new jurist, at the fulcrum of Trump's efforts to change life in America," Joan Biskupic, CNN legal analyst and Supreme Court biographer, wrote Tuesday.
Trump's order last Friday temporarily barring refugees and citizens from seven Muslim-majority countries from entering the country resulted in massive protests and a flurry of litigation in which lower court judges temporarily suspended parts of the order.
Trump — whose Republican Party controls both Houses of Congress — fired acting Attorney General Sally Yates on Monday after she told Justice Department lawyers not to defend the order in the wake of rulings against it.
More than 40 lawsuits have been filed against Trump in the first week of his presidency, including three by states challenging the legality of the immigration ban.
"Rarely has there been a moment in American history of such widespread national discord, internal court divisions, and the opportunity for a new tie-breaking justice," Biskupic wrote.
Does the ideological makeup of the court matter?
The nine-member court is deeply divided along ideological lines. Every vote matters. The dissent of a lone justice can tip the balance on major issues involving civil rights and criminal law.
While the overwhelming number of past decisions have had implications for Americans alone, others have resounded internationally.
The Supreme Court ultimately decided who won the 2000 presidential election, George W. Bush or Al Gore, even though the controversy lingers.
What's the makeup of the current court?
Four Republican appointees on the bench have generally taken a conservative stance (Chief Justice John Roberts and Justices Anthony Kennedy, Clarence Thomas and Samuel Alito) and four Democratic appointees regularly have been more liberal (Justices Ruth Bader Ginsburg, Stephen Breyer, Sonia Sotomayor and Elena Kagan).
Under Scalia, the court was one of the most conservative in modern times. His successor will take the place of a rigid conservative on issues such as abortion rights, affirmative action and gay marriage.
Trump has expressed his desire for a justice who would reverse Roe v. Wade, which made abortion legal nationwide. He has said he wants states to have the power to determine when a woman has the right to end a pregnancy.
Kennedy's centrist tendencies prevented conservatives from significantly rolling back abortion rights, or race-based policies intended to enhance student diversity at universities -- as allowed in 1978 by Regents of the University of California v. Bakke. Kennedy was also the crucial fifth vote to declare a constitutional right to same-sex marriage in 2015.
He remains on the bench, but he is 80 years old and has indicated to some close friends and associates an interest in retiring. If he were to step down, successive nominations by Trump could transform the court and the law in America.
Ginsburg, who will turn 84 in March, is the court's eldest justice. Breyer will turn 79 in August.
What is the primary purpose of the court?
The first meeting of the Supreme Court was in 1790. The justices serve as the final word for a nation built on the rule of law.
The court is led by the Chief Justice of the United States (that's the official title). All justices -- and all federal judges -- are first nominated by the president and must be confirmed by the Senate. They serve for as long as they choose.
The justices interpret the Constitution, which involves every aspect of American's lives -- how they conduct themselves in society and boundaries for individuals and the government.
As the late justice William Brennan once wrote: "The law is not an end in itself, nor does it provide ends. It is preeminently a means to serve what we think is right."
How does the court work?
Traditionally, each Supreme Court term begins the first Monday in October, and final opinions are issued usually by late June.
The justices divide their time between "sittings," where they hear cases and issue decisions, and "recesses," where they meet in private to write their decisions and consider other business before the court.
The justices are seated by seniority, with the chief justice in the middle. The two junior justices (currently Sotomayor and Kagan) occupy the opposite ends of the bench.
Arguments usually begin at 10 a.m. and since most cases involve appellate review of decisions by other courts, there are no juries or witnesses, just lawyers from both sides addressing the bench. The cases usually last about an hour. Lawyers from both sides very often have their prepared oral briefs interrupted by pointed questions from a justice.
How many cases are accepted?
Each week, the court receives more than 150 petitions for review -- decisions by lower courts appealed to the high court. Relatively few are granted full review. About 8,000 to 10,000 such petitions go on the court's docket each term.
Only 75 to 85 cases -- about 1% -- are accepted.
Court opinions are final. The only exception is the court itself, which can over time overturn its own precedent, as it did with racial segregation. But most justices rely on the principle of "stare decisis," Latin for "to stand by a decision," where a current court should be bound by previous rulings.