Advancement in radio technology means that radio astronomy has to share the radio spectrum with many other non-astronomical activities, majority of which increase radio frequency interference (RFI), and therefore detrimentally affecting the radio observations at the observatory sites. Major radio facilities such as the SKA, in both South Africa and Australia, and the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in China will be very sensitive, and therefore require protection against RFI.
In the case of optical astronomy, the growing urbanisation and industrialisation led to optical astronomy becoming impossible near major cities due to light and dust pollution. Major optical and IR observatories are forced to be far away in remote areas, where light pollution is not yet extreme. The same is true for radio observatories, which have to be sited away from highly RFI affected areas near populated regions and major cities.
In this review, based on the Focus Meeting 21 (FM21) oral presentations at the IAU General Assembly on 11 August 2015, we give an overview of the mechanisms that have evolved to provide statutory protection for radio astronomy observing, successes (e.g at 21 cm HI line), defeats and challenges at other parts of the spectrum. We discuss the available legislative initiatives to protect the radio astronomy sites for large projects like SKA (in Australia and South Africa), and FAST against the RFI. For optical protection, we look at light pollution with examples of its effect at Xinglong observing station of the National Astronomical Observatories of China (NAOC), Ali Observatory in Tibet, and Asiago Observatory in Italy, as well as the effect of conversion from low pressure sodium lighting to LEDs in the County of Hawaii.