What is the Shar'i (Islamic legal) ruling on a man urinating while standing, and is it haram (forbidden) based on the hadith of 'Aisha (may Allah be pleased with her): "Whoever tells you that the Prophet (peace and blessings of Allah be upon him) urinated while standing, do not believe him"?

Urination while standing is not forbidden, but it is preferable to urinate while sitting. Permission has been granted for urinating while standing if a Muslim is safe from urine splashing and exposure of his 'awrah (private parts). This is based on what Al-Bukhari and Muslim narrated from Hudhayfah, that the Prophet (peace and blessings be upon him) "came to a قوم's dunghill and urinated while standing." This does not contradict the hadith (definition) of 'Aishah that the Prophet (peace and blessings be upon him) never urinated except while sitting, as it is possible that he did so due to inability to sit or to demonstrate permissibility.