The constitution does not define "natural born", so the historical context must be used in order to understand its context. The founders wanted to be sure that there were no other loyalties other than that of the United States. Dual citizens therefore must be excluded as natural born. Immigrants can be naturalized, and later become citizens, but are not natural born citizens. Current US law clearly states: "If only one parent was a U.S. citizen at the time of your birth, that parent must have resided in the United States for at least ten years, at least five of which had to be after the age of 16". Doing the math, this means that you must be 21 years old and have spent that last 5 years in the united states. If this is not the case, the child cannot vote until later naturalized. This means that the child assumes the nationality of the non-citizen parent. Also, the child must be born on United States soil ( One of the states, territories, military base, or within a United States consulate).
This should also mean that illegal aliens must not be granted citizenship even when born within United States soil as neither parent is a citizen of the United States. Current policy must be changed to enforce this rule.
Unfortunately, there is no federal provision, regulatory power, or other statute that is responsible for checking the eligibility. This means that such responsibility must be assumed by each state in the union. Up to now, there has not been a need to create such a law, statute, or regulatory power. The constitution does not detail how to resolve such a violation of eligibility.
Such a violation could potentially be handled by the supreme court. The violator would simply be forced to step down, as he is in clear violation of the Constitution. What happens to all of the laws, executive orders, and actions signed by the imposter? This is anyone's guess. The inefficiency and backlog of the courts could mean that a person could potentially serve full term without being removed from office. Typically laws are only created after someone does something unexpected.
If the supreme court is unwilling or unable to remove an unqualified person from office, he must be impeached by the house of representatives and tried by the senate; the chief justice of the supreme court must preside over the trial.
There is strong evidence that Obama is not eligible to be president of the United States. The newly issued long-form certificate of live birth is a poorly constructed forgery. Just watch one of several hundred demonstrations (from YouTube) that detail this fact. Some of the anomalies also exist on the original short form which also happens to be a forgery. A forged birth certificate does not constitute proof of natural born citizen status. Note that as Obama has publically endorsed these forgeries as his birth credentials, he has committed a felony. This act alone deserves impeachment.
Note that the senate is controlled by democrats, so impeachment will not work. Even though each senator is sworn to be impartial, they typically vote along party lines as was done during the Clinton trial.
A better plan of attack is to remain as silent as the mainstream media, and let Obama win the nomination. In the mean time, each state must enact law that forbids candidates from being placed on the ballot without proof of eligibility. This means that Obama will need to be a "write in" candidate for that state. When that happens, even the mainstream media will have to report this event.