Its decisions restrict what laws can be made, and while not technically "laws" (as the term is applied to mandates passed by Congress). By narrowly restricting how laws can be made, it effectively creates laws.
The Constitution says the Supreme Court is the "supreme law of the land". But yes, technically I did not answer his question.
Um, no it doesn't. The constitutions says that IT is the supreme law of the land. The constitution doesn't even grant the Supreme Court the power to judge the constitutionality of laws, that's just something that they assumed they could do, and there isn't really any court capable of overridding that assumption. Technically, the House of Representives has the power to sensor/override a Supreme court ruling; but this has actually never occured.