I was wondering if the weather is required at an airport for ATC to issue an IFR approach clearance to that airport. For instance, Lets say that airborn pilot reports indicate that the weather is clear and a million, however a non-towered airport's ASOS or AWOS is out of service. Can ATC clear a pilot for a precision or non precision approach to that airport? I don't think they can because there needs to be an altimeter setting... not to mention part 135 and 121 MUST have the minimum visibility reported on the field prior to passing the FAF. What are your thoughts on this...especially ATC guys. Any regs that spell this out would be appreciated. Thanks in advance for any serious answers.